| Message ID | 1329519726-25763-2-git-send-email-aliguori@us.ibm.com |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: > This patch allows vhost to have multiple worker threads for devices such as > virtio-net which may have multiple virtqueues. > > Since virtqueues are a lockless ring queue, in an ideal world data is being > produced by the producer as fast as data is being consumed by the consumer. > These loops will continue to consume data until none is left. > > vhost currently multiplexes the consumer side of the queue on a single thread > by attempting to read from the queue until everything is read or it cannot > process anymore. This means that activity on one queue may stall another queue. There's actually an attempt to address this: look up VHOST_NET_WEIGHT in the code. I take it, this isn't effective? > This is exacerbated when using any form of polling to read from the queues (as > we'll introduce in the next patch). By spawning a thread per-virtqueue, this > is addressed. > > The only problem with this patch right now is how the wake up of the threads is > done. It's essentially a broadcast and we have seen lock contention as a > result. On which lock? > We've tried some approaches to signal a single thread but I'm not > confident that that code is correct yet so I'm only sending the broadcast > version. Yes, that looks like an obvious question. > Here are some performance results from this change. There's a modest > improvement with stream although a fair bit of variability too. > > With RR, there's pretty significant improvements as the instance rate drives up. Interesting. This was actually tested at one time and we saw a significant performance improvement from using a single thread especially with a single stream in the guest. Profiling indicated that with a single thread we get too many context switches between TX and RX, since guest networking tends to run TX and RX processing on the same guest VCPU. Maybe we were wrong or maybe this went away for some reason. I'll see if this can be reproduced. > > Test, Size, Instance, Baseline, Patch, Relative > > TCP_RR > Tx:256 Rx:256 > 1 9,639.66 10,164.06 105.44% > 10 62,819.55 54,059.78 86.06% > 30 84,715.60 131,241.86 154.92% > 60 124,614.71 148,720.66 119.34% > > UDP_RR > Tx:256 Rx:256 > 1 9,652.50 10,343.72 107.16% > 10 53,830.26 58,235.90 108.18% > 30 89,471.01 97,634.53 109.12% > 60 103,640.59 164,035.01 158.27% > > TCP_STREAM > Tx: 256 > 1 2,622.63 2,610.71 99.55% > 4 4,928.02 4,812.05 97.65% > > Tx: 1024 > 1 5,639.89 5,751.28 101.97% > 4 5,874.72 6,575.55 111.93% > > Tx: 4096 > 1 6,257.42 7,655.22 122.34% > 4 5,370.78 6,044.83 112.55% > > Tx: 16384 > 1 6,346.63 7,267.44 114.51% > 4 5,198.02 5,657.12 108.83% > > TCP_MAERTS > Rx: 256 > 1 2,091.38 1,765.62 84.42% > 4 5,319.52 5,619.49 105.64% > > Rx: 1024 > 1 7,030.66 7,593.61 108.01% > 4 9,040.53 7,275.84 80.48% > > Rx: 4096 > 1 9,160.93 9,318.15 101.72% > 4 9,372.49 8,875.63 94.70% > > Rx: 16384 > 1 9,183.28 9,134.02 99.46% > 4 9,377.17 8,877.52 94.67% > > 106.46% One point missing here is the ratio of throughput divided by host CPU utilization. The concern being to avoid hurting heavily loaded systems. These numbers also tend to be less variable as they depend less on host scheduler decisions. > Cc: Tom Lendacky <toml@us.ibm.com> > Cc: Cristian Viana <vianac@br.ibm.com> > Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> > --- > drivers/vhost/net.c | 6 ++++- > drivers/vhost/vhost.c | 51 ++++++++++++++++++++++++++++++------------------ > drivers/vhost/vhost.h | 8 +++++- > 3 files changed, 43 insertions(+), 22 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 9dab1f5..47175cd 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -33,6 +33,10 @@ static int experimental_zcopytx; > module_param(experimental_zcopytx, int, 0444); > MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX"); > > +static int workers = 2; > +module_param(workers, int, 0444); > +MODULE_PARM_DESC(workers, "Set the number of worker threads"); > + > /* Max number of bytes transferred before requeueing the job. > * Using this limit prevents one virtqueue from starving others. */ > #define VHOST_NET_WEIGHT 0x80000 > @@ -504,7 +508,7 @@ static int vhost_net_open(struct inode *inode, struct file *f) > dev = &n->dev; > n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick; > n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick; > - r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX); > + r = vhost_dev_init(dev, n->vqs, workers, VHOST_NET_VQ_MAX); > if (r < 0) { > kfree(n); > return r; > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index c14c42b..676cead 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -144,9 +144,12 @@ static inline void vhost_work_queue(struct vhost_dev *dev, > > spin_lock_irqsave(&dev->work_lock, flags); > if (list_empty(&work->node)) { > + int i; > + > list_add_tail(&work->node, &dev->work_list); > work->queue_seq++; > - wake_up_process(dev->worker); > + for (i = 0; i < dev->nworkers; i++) > + wake_up_process(dev->workers[i]); > } > spin_unlock_irqrestore(&dev->work_lock, flags); > } > @@ -287,7 +290,7 @@ static void vhost_dev_free_iovecs(struct vhost_dev *dev) > } > > long vhost_dev_init(struct vhost_dev *dev, > - struct vhost_virtqueue *vqs, int nvqs) > + struct vhost_virtqueue *vqs, int nworkers, int nvqs) > { > int i; > > @@ -300,7 +303,9 @@ long vhost_dev_init(struct vhost_dev *dev, > dev->mm = NULL; > spin_lock_init(&dev->work_lock); > INIT_LIST_HEAD(&dev->work_list); > - dev->worker = NULL; > + dev->nworkers = min(nworkers, VHOST_MAX_WORKERS); > + for (i = 0; i < dev->nworkers; i++) > + dev->workers[i] = NULL; > > for (i = 0; i < dev->nvqs; ++i) { > dev->vqs[i].log = NULL; > @@ -354,7 +359,7 @@ static int vhost_attach_cgroups(struct vhost_dev *dev) > static long vhost_dev_set_owner(struct vhost_dev *dev) > { > struct task_struct *worker; > - int err; > + int err, i; > > /* Is there an owner already? */ > if (dev->mm) { > @@ -364,28 +369,34 @@ static long vhost_dev_set_owner(struct vhost_dev *dev) > > /* No owner, become one */ > dev->mm = get_task_mm(current); > - worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid); > - if (IS_ERR(worker)) { > - err = PTR_ERR(worker); > - goto err_worker; > - } > + for (i = 0; i < dev->nworkers; i++) { > + worker = kthread_create(vhost_worker, dev, "vhost-%d.%d", current->pid, i); > + if (IS_ERR(worker)) { > + err = PTR_ERR(worker); > + goto err_worker; > + } > > - dev->worker = worker; > - wake_up_process(worker); /* avoid contributing to loadavg */ > + dev->workers[i] = worker; > + wake_up_process(worker); /* avoid contributing to loadavg */ > + } > > err = vhost_attach_cgroups(dev); > if (err) > - goto err_cgroup; > + goto err_worker; > > err = vhost_dev_alloc_iovecs(dev); > if (err) > - goto err_cgroup; > + goto err_worker; > > return 0; > -err_cgroup: > - kthread_stop(worker); > - dev->worker = NULL; > + > err_worker: > + for (i = 0; i < dev->nworkers; i++) { > + if (dev->workers[i]) { > + kthread_stop(dev->workers[i]); > + dev->workers[i] = NULL; > + } > + } > if (dev->mm) > mmput(dev->mm); > dev->mm = NULL; > @@ -475,9 +486,11 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > lockdep_is_held(&dev->mutex))); > RCU_INIT_POINTER(dev->memory, NULL); > WARN_ON(!list_empty(&dev->work_list)); > - if (dev->worker) { > - kthread_stop(dev->worker); > - dev->worker = NULL; > + for (i = 0; i < dev->nworkers; i++) { > + if (dev->workers[i]) { > + kthread_stop(dev->workers[i]); > + dev->workers[i] = NULL; > + } > } > if (dev->mm) > mmput(dev->mm); > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index a801e28..fa5e75e 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -18,6 +18,9 @@ > #define VHOST_DMA_DONE_LEN 1 > #define VHOST_DMA_CLEAR_LEN 0 > > +/* Maximum number of worker threads per-vhost device */ > +#define VHOST_MAX_WORKERS 8 > + > struct vhost_device; > > struct vhost_work; > @@ -157,10 +160,11 @@ struct vhost_dev { > struct eventfd_ctx *log_ctx; > spinlock_t work_lock; > struct list_head work_list; > - struct task_struct *worker; > + int nworkers; > + struct task_struct *workers[VHOST_MAX_WORKERS]; > }; > > -long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs); > +long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nworkers, int nvqs); > long vhost_dev_check_owner(struct vhost_dev *); > long vhost_dev_reset_owner(struct vhost_dev *); > void vhost_dev_cleanup(struct vhost_dev *); > -- > 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
"Michael S. Tsirkin" <mst@redhat.com> wrote on 02/19/2012 08:41:45 AM: > From: "Michael S. Tsirkin" <mst@redhat.com> > To: Anthony Liguori/Austin/IBM@IBMUS > Cc: netdev@vger.kernel.org, Tom Lendacky/Austin/IBM@IBMUS, Cristian > Viana <vianac@br.ibm.com> > Date: 02/19/2012 08:42 AM > Subject: Re: [PATCH 1/2] vhost: allow multiple workers threads > > On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: > > This patch allows vhost to have multiple worker threads for devices such as > > virtio-net which may have multiple virtqueues. > > > > Since virtqueues are a lockless ring queue, in an ideal world data is being > > produced by the producer as fast as data is being consumed by the consumer. > > These loops will continue to consume data until none is left. > > > > vhost currently multiplexes the consumer side of the queue on a > single thread > > by attempting to read from the queue until everything is read or it cannot > > process anymore. This means that activity on one queue may stall > another queue. > > There's actually an attempt to address this: look up > VHOST_NET_WEIGHT in the code. I take it, this isn't effective? > > > This is exacerbated when using any form of polling to read from > the queues (as > > we'll introduce in the next patch). By spawning a thread per- > virtqueue, this > > is addressed. > > > > The only problem with this patch right now is how the wake up of > the threads is > > done. It's essentially a broadcast and we have seen lock contention as a > > result. > > On which lock? The mutex lock in the vhost_virtqueue struct. This really shows up when running with patch 2/2 and increasing the spin_threshold. Both threads wake up and try to acquire the mutex. As the spin_threshold increases you end up with one of the threads getting blocked for a longer and longer time and unable to do any RX processing that might be needed. Tom > > > We've tried some approaches to signal a single thread but I'm not > > confident that that code is correct yet so I'm only sending the broadcast > > version. > > Yes, that looks like an obvious question. > > > Here are some performance results from this change. There's a modest > > improvement with stream although a fair bit of variability too. > > > > With RR, there's pretty significant improvements as the instance > rate drives up. > > Interesting. This was actually tested at one time and we saw > a significant performance improvement from using > a single thread especially with a single > stream in the guest. Profiling indicated that > with a single thread we get too many context > switches between TX and RX, since guest networking > tends to run TX and RX processing on the same > guest VCPU. > > Maybe we were wrong or maybe this went away > for some reason. I'll see if this can be reproduced. > > > > > Test, Size, Instance, Baseline, Patch, Relative > > > > TCP_RR > > Tx:256 Rx:256 > > 1 9,639.66 10,164.06 105.44% > > 10 62,819.55 54,059.78 86.06% > > 30 84,715.60 131,241.86 154.92% > > 60 124,614.71 148,720.66 119.34% > > > > UDP_RR > > Tx:256 Rx:256 > > 1 9,652.50 10,343.72 107.16% > > 10 53,830.26 58,235.90 108.18% > > 30 89,471.01 97,634.53 109.12% > > 60 103,640.59 164,035.01 158.27% > > > > TCP_STREAM > > Tx: 256 > > 1 2,622.63 2,610.71 99.55% > > 4 4,928.02 4,812.05 97.65% > > > > Tx: 1024 > > 1 5,639.89 5,751.28 101.97% > > 4 5,874.72 6,575.55 111.93% > > > > Tx: 4096 > > 1 6,257.42 7,655.22 122.34% > > 4 5,370.78 6,044.83 112.55% > > > > Tx: 16384 > > 1 6,346.63 7,267.44 114.51% > > 4 5,198.02 5,657.12 108.83% > > > > TCP_MAERTS > > Rx: 256 > > 1 2,091.38 1,765.62 84.42% > > 4 5,319.52 5,619.49 105.64% > > > > Rx: 1024 > > 1 7,030.66 7,593.61 108.01% > > 4 9,040.53 7,275.84 80.48% > > > > Rx: 4096 > > 1 9,160.93 9,318.15 101.72% > > 4 9,372.49 8,875.63 94.70% > > > > Rx: 16384 > > 1 9,183.28 9,134.02 99.46% > > 4 9,377.17 8,877.52 94.67% > > > > 106.46% > > One point missing here is the ratio of > throughput divided by host CPU utilization. > > The concern being to avoid hurting > heavily loaded systems. > > These numbers also tend to be less variable as > they depend less on host scheduler decisions. > > > > Cc: Tom Lendacky <toml@us.ibm.com> > > Cc: Cristian Viana <vianac@br.ibm.com> > > Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> > > --- > > drivers/vhost/net.c | 6 ++++- > > drivers/vhost/vhost.c | 51 +++++++++++++++++++++++++++++ > +------------------ > > drivers/vhost/vhost.h | 8 +++++- > > 3 files changed, 43 insertions(+), 22 deletions(-) > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > index 9dab1f5..47175cd 100644 > > --- a/drivers/vhost/net.c > > +++ b/drivers/vhost/net.c > > @@ -33,6 +33,10 @@ static int experimental_zcopytx; > > module_param(experimental_zcopytx, int, 0444); > > MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX"); > > > > +static int workers = 2; > > +module_param(workers, int, 0444); > > +MODULE_PARM_DESC(workers, "Set the number of worker threads"); > > + > > /* Max number of bytes transferred before requeueing the job. > > * Using this limit prevents one virtqueue from starving others. */ > > #define VHOST_NET_WEIGHT 0x80000 > > @@ -504,7 +508,7 @@ static int vhost_net_open(struct inode *inode, > struct file *f) > > dev = &n->dev; > > n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick; > > n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick; > > - r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX); > > + r = vhost_dev_init(dev, n->vqs, workers, VHOST_NET_VQ_MAX); > > if (r < 0) { > > kfree(n); > > return r; > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index c14c42b..676cead 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -144,9 +144,12 @@ static inline void vhost_work_queue(struct > vhost_dev *dev, > > > > spin_lock_irqsave(&dev->work_lock, flags); > > if (list_empty(&work->node)) { > > + int i; > > + > > list_add_tail(&work->node, &dev->work_list); > > work->queue_seq++; > > - wake_up_process(dev->worker); > > + for (i = 0; i < dev->nworkers; i++) > > + wake_up_process(dev->workers[i]); > > } > > spin_unlock_irqrestore(&dev->work_lock, flags); > > } > > @@ -287,7 +290,7 @@ static void vhost_dev_free_iovecs(struct vhost_dev *dev) > > } > > > > long vhost_dev_init(struct vhost_dev *dev, > > - struct vhost_virtqueue *vqs, int nvqs) > > + struct vhost_virtqueue *vqs, int nworkers, int nvqs) > > { > > int i; > > > > @@ -300,7 +303,9 @@ long vhost_dev_init(struct vhost_dev *dev, > > dev->mm = NULL; > > spin_lock_init(&dev->work_lock); > > INIT_LIST_HEAD(&dev->work_list); > > - dev->worker = NULL; > > + dev->nworkers = min(nworkers, VHOST_MAX_WORKERS); > > + for (i = 0; i < dev->nworkers; i++) > > + dev->workers[i] = NULL; > > > > for (i = 0; i < dev->nvqs; ++i) { > > dev->vqs[i].log = NULL; > > @@ -354,7 +359,7 @@ static int vhost_attach_cgroups(struct vhost_dev *dev) > > static long vhost_dev_set_owner(struct vhost_dev *dev) > > { > > struct task_struct *worker; > > - int err; > > + int err, i; > > > > /* Is there an owner already? */ > > if (dev->mm) { > > @@ -364,28 +369,34 @@ static long vhost_dev_set_owner(struct vhost_dev *dev) > > > > /* No owner, become one */ > > dev->mm = get_task_mm(current); > > - worker = kthread_create(vhost_worker, dev, "vhost-%d", current-> pid); > > - if (IS_ERR(worker)) { > > - err = PTR_ERR(worker); > > - goto err_worker; > > - } > > + for (i = 0; i < dev->nworkers; i++) { > > + worker = kthread_create(vhost_worker, dev, "vhost-%d.%d", > current->pid, i); > > + if (IS_ERR(worker)) { > > + err = PTR_ERR(worker); > > + goto err_worker; > > + } > > > > - dev->worker = worker; > > - wake_up_process(worker); /* avoid contributing to loadavg */ > > + dev->workers[i] = worker; > > + wake_up_process(worker); /* avoid contributing to loadavg */ > > + } > > > > err = vhost_attach_cgroups(dev); > > if (err) > > - goto err_cgroup; > > + goto err_worker; > > > > err = vhost_dev_alloc_iovecs(dev); > > if (err) > > - goto err_cgroup; > > + goto err_worker; > > > > return 0; > > -err_cgroup: > > - kthread_stop(worker); > > - dev->worker = NULL; > > + > > err_worker: > > + for (i = 0; i < dev->nworkers; i++) { > > + if (dev->workers[i]) { > > + kthread_stop(dev->workers[i]); > > + dev->workers[i] = NULL; > > + } > > + } > > if (dev->mm) > > mmput(dev->mm); > > dev->mm = NULL; > > @@ -475,9 +486,11 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > > lockdep_is_held(&dev->mutex))); > > RCU_INIT_POINTER(dev->memory, NULL); > > WARN_ON(!list_empty(&dev->work_list)); > > - if (dev->worker) { > > - kthread_stop(dev->worker); > > - dev->worker = NULL; > > + for (i = 0; i < dev->nworkers; i++) { > > + if (dev->workers[i]) { > > + kthread_stop(dev->workers[i]); > > + dev->workers[i] = NULL; > > + } > > } > > if (dev->mm) > > mmput(dev->mm); > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index a801e28..fa5e75e 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -18,6 +18,9 @@ > > #define VHOST_DMA_DONE_LEN 1 > > #define VHOST_DMA_CLEAR_LEN 0 > > > > +/* Maximum number of worker threads per-vhost device */ > > +#define VHOST_MAX_WORKERS 8 > > + > > struct vhost_device; > > > > struct vhost_work; > > @@ -157,10 +160,11 @@ struct vhost_dev { > > struct eventfd_ctx *log_ctx; > > spinlock_t work_lock; > > struct list_head work_list; > > - struct task_struct *worker; > > + int nworkers; > > + struct task_struct *workers[VHOST_MAX_WORKERS]; > > }; > > > > -long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue > *vqs, int nvqs); > > +long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue > *vqs, int nworkers, int nvqs); > > long vhost_dev_check_owner(struct vhost_dev *); > > long vhost_dev_reset_owner(struct vhost_dev *); > > void vhost_dev_cleanup(struct vhost_dev *); > > -- > > 1.7.4.1 > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Feb 20, 2012 at 09:50:37AM -0600, Tom Lendacky wrote: > "Michael S. Tsirkin" <mst@redhat.com> wrote on 02/19/2012 08:41:45 AM: > > > From: "Michael S. Tsirkin" <mst@redhat.com> > > To: Anthony Liguori/Austin/IBM@IBMUS > > Cc: netdev@vger.kernel.org, Tom Lendacky/Austin/IBM@IBMUS, Cristian > > Viana <vianac@br.ibm.com> > > Date: 02/19/2012 08:42 AM > > Subject: Re: [PATCH 1/2] vhost: allow multiple workers threads > > > > On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: > > > This patch allows vhost to have multiple worker threads for devices > such as > > > virtio-net which may have multiple virtqueues. > > > > > > Since virtqueues are a lockless ring queue, in an ideal world data is > being > > > produced by the producer as fast as data is being consumed by the > consumer. > > > These loops will continue to consume data until none is left. > > > > > > vhost currently multiplexes the consumer side of the queue on a > > single thread > > > by attempting to read from the queue until everything is read or it > cannot > > > process anymore. This means that activity on one queue may stall > > another queue. > > > > There's actually an attempt to address this: look up > > VHOST_NET_WEIGHT in the code. I take it, this isn't effective? > > > > > This is exacerbated when using any form of polling to read from > > the queues (as > > > we'll introduce in the next patch). By spawning a thread per- > > virtqueue, this > > > is addressed. > > > > > > The only problem with this patch right now is how the wake up of > > the threads is > > > done. It's essentially a broadcast and we have seen lock contention as > a > > > result. > > > > On which lock? > > The mutex lock in the vhost_virtqueue struct. This really shows up when > running with patch 2/2 and increasing the spin_threshold. Both threads wake > up and try to acquire the mutex. As the spin_threshold increases you end > up > with one of the threads getting blocked for a longer and longer time and > unable to do any RX processing that might be needed. > > Tom Weird, I had the impression each thread handles one vq. Isn't this the design? > > > > > We've tried some approaches to signal a single thread but I'm not > > > confident that that code is correct yet so I'm only sending the > broadcast > > > version. > > > > Yes, that looks like an obvious question. > > > > > Here are some performance results from this change. There's a modest > > > improvement with stream although a fair bit of variability too. > > > > > > With RR, there's pretty significant improvements as the instance > > rate drives up. > > > > Interesting. This was actually tested at one time and we saw > > a significant performance improvement from using > > a single thread especially with a single > > stream in the guest. Profiling indicated that > > with a single thread we get too many context > > switches between TX and RX, since guest networking > > tends to run TX and RX processing on the same > > guest VCPU. > > > > Maybe we were wrong or maybe this went away > > for some reason. I'll see if this can be reproduced. > > > > > > > > Test, Size, Instance, Baseline, Patch, Relative > > > > > > TCP_RR > > > Tx:256 Rx:256 > > > 1 9,639.66 10,164.06 105.44% > > > 10 62,819.55 54,059.78 86.06% > > > 30 84,715.60 131,241.86 154.92% > > > 60 124,614.71 148,720.66 119.34% > > > > > > UDP_RR > > > Tx:256 Rx:256 > > > 1 9,652.50 10,343.72 107.16% > > > 10 53,830.26 58,235.90 108.18% > > > 30 89,471.01 97,634.53 109.12% > > > 60 103,640.59 164,035.01 158.27% > > > > > > TCP_STREAM > > > Tx: 256 > > > 1 2,622.63 2,610.71 99.55% > > > 4 4,928.02 4,812.05 97.65% > > > > > > Tx: 1024 > > > 1 5,639.89 5,751.28 101.97% > > > 4 5,874.72 6,575.55 111.93% > > > > > > Tx: 4096 > > > 1 6,257.42 7,655.22 122.34% > > > 4 5,370.78 6,044.83 112.55% > > > > > > Tx: 16384 > > > 1 6,346.63 7,267.44 114.51% > > > 4 5,198.02 5,657.12 108.83% > > > > > > TCP_MAERTS > > > Rx: 256 > > > 1 2,091.38 1,765.62 84.42% > > > 4 5,319.52 5,619.49 105.64% > > > > > > Rx: 1024 > > > 1 7,030.66 7,593.61 108.01% > > > 4 9,040.53 7,275.84 80.48% > > > > > > Rx: 4096 > > > 1 9,160.93 9,318.15 101.72% > > > 4 9,372.49 8,875.63 94.70% > > > > > > Rx: 16384 > > > 1 9,183.28 9,134.02 99.46% > > > 4 9,377.17 8,877.52 94.67% > > > > > > 106.46% > > > > One point missing here is the ratio of > > throughput divided by host CPU utilization. > > > > The concern being to avoid hurting > > heavily loaded systems. > > > > These numbers also tend to be less variable as > > they depend less on host scheduler decisions. > > > > > > > Cc: Tom Lendacky <toml@us.ibm.com> > > > Cc: Cristian Viana <vianac@br.ibm.com> > > > Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> > > > --- > > > drivers/vhost/net.c | 6 ++++- > > > drivers/vhost/vhost.c | 51 +++++++++++++++++++++++++++++ > > +------------------ > > > drivers/vhost/vhost.h | 8 +++++- > > > 3 files changed, 43 insertions(+), 22 deletions(-) > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > index 9dab1f5..47175cd 100644 > > > --- a/drivers/vhost/net.c > > > +++ b/drivers/vhost/net.c > > > @@ -33,6 +33,10 @@ static int experimental_zcopytx; > > > module_param(experimental_zcopytx, int, 0444); > > > MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy > TX"); > > > > > > +static int workers = 2; > > > +module_param(workers, int, 0444); > > > +MODULE_PARM_DESC(workers, "Set the number of worker threads"); > > > + > > > /* Max number of bytes transferred before requeueing the job. > > > * Using this limit prevents one virtqueue from starving others. */ > > > #define VHOST_NET_WEIGHT 0x80000 > > > @@ -504,7 +508,7 @@ static int vhost_net_open(struct inode *inode, > > struct file *f) > > > dev = &n->dev; > > > n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick; > > > n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick; > > > - r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX); > > > + r = vhost_dev_init(dev, n->vqs, workers, VHOST_NET_VQ_MAX); > > > if (r < 0) { > > > kfree(n); > > > return r; > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index c14c42b..676cead 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -144,9 +144,12 @@ static inline void vhost_work_queue(struct > > vhost_dev *dev, > > > > > > spin_lock_irqsave(&dev->work_lock, flags); > > > if (list_empty(&work->node)) { > > > + int i; > > > + > > > list_add_tail(&work->node, &dev->work_list); > > > work->queue_seq++; > > > - wake_up_process(dev->worker); > > > + for (i = 0; i < dev->nworkers; i++) > > > + wake_up_process(dev->workers[i]); > > > } > > > spin_unlock_irqrestore(&dev->work_lock, flags); > > > } > > > @@ -287,7 +290,7 @@ static void vhost_dev_free_iovecs(struct vhost_dev > *dev) > > > } > > > > > > long vhost_dev_init(struct vhost_dev *dev, > > > - struct vhost_virtqueue *vqs, int nvqs) > > > + struct vhost_virtqueue *vqs, int nworkers, int nvqs) > > > { > > > int i; > > > > > > @@ -300,7 +303,9 @@ long vhost_dev_init(struct vhost_dev *dev, > > > dev->mm = NULL; > > > spin_lock_init(&dev->work_lock); > > > INIT_LIST_HEAD(&dev->work_list); > > > - dev->worker = NULL; > > > + dev->nworkers = min(nworkers, VHOST_MAX_WORKERS); > > > + for (i = 0; i < dev->nworkers; i++) > > > + dev->workers[i] = NULL; > > > > > > for (i = 0; i < dev->nvqs; ++i) { > > > dev->vqs[i].log = NULL; > > > @@ -354,7 +359,7 @@ static int vhost_attach_cgroups(struct vhost_dev > *dev) > > > static long vhost_dev_set_owner(struct vhost_dev *dev) > > > { > > > struct task_struct *worker; > > > - int err; > > > + int err, i; > > > > > > /* Is there an owner already? */ > > > if (dev->mm) { > > > @@ -364,28 +369,34 @@ static long vhost_dev_set_owner(struct vhost_dev > *dev) > > > > > > /* No owner, become one */ > > > dev->mm = get_task_mm(current); > > > - worker = kthread_create(vhost_worker, dev, "vhost-%d", current-> > pid); > > > - if (IS_ERR(worker)) { > > > - err = PTR_ERR(worker); > > > - goto err_worker; > > > - } > > > + for (i = 0; i < dev->nworkers; i++) { > > > + worker = kthread_create(vhost_worker, dev, "vhost-%d.%d", > > current->pid, i); > > > + if (IS_ERR(worker)) { > > > + err = PTR_ERR(worker); > > > + goto err_worker; > > > + } > > > > > > - dev->worker = worker; > > > - wake_up_process(worker); /* avoid contributing to loadavg */ > > > + dev->workers[i] = worker; > > > + wake_up_process(worker); /* avoid contributing to loadavg */ > > > + } > > > > > > err = vhost_attach_cgroups(dev); > > > if (err) > > > - goto err_cgroup; > > > + goto err_worker; > > > > > > err = vhost_dev_alloc_iovecs(dev); > > > if (err) > > > - goto err_cgroup; > > > + goto err_worker; > > > > > > return 0; > > > -err_cgroup: > > > - kthread_stop(worker); > > > - dev->worker = NULL; > > > + > > > err_worker: > > > + for (i = 0; i < dev->nworkers; i++) { > > > + if (dev->workers[i]) { > > > + kthread_stop(dev->workers[i]); > > > + dev->workers[i] = NULL; > > > + } > > > + } > > > if (dev->mm) > > > mmput(dev->mm); > > > dev->mm = NULL; > > > @@ -475,9 +486,11 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > > > lockdep_is_held(&dev->mutex))); > > > RCU_INIT_POINTER(dev->memory, NULL); > > > WARN_ON(!list_empty(&dev->work_list)); > > > - if (dev->worker) { > > > - kthread_stop(dev->worker); > > > - dev->worker = NULL; > > > + for (i = 0; i < dev->nworkers; i++) { > > > + if (dev->workers[i]) { > > > + kthread_stop(dev->workers[i]); > > > + dev->workers[i] = NULL; > > > + } > > > } > > > if (dev->mm) > > > mmput(dev->mm); > > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > > index a801e28..fa5e75e 100644 > > > --- a/drivers/vhost/vhost.h > > > +++ b/drivers/vhost/vhost.h > > > @@ -18,6 +18,9 @@ > > > #define VHOST_DMA_DONE_LEN 1 > > > #define VHOST_DMA_CLEAR_LEN 0 > > > > > > +/* Maximum number of worker threads per-vhost device */ > > > +#define VHOST_MAX_WORKERS 8 > > > + > > > struct vhost_device; > > > > > > struct vhost_work; > > > @@ -157,10 +160,11 @@ struct vhost_dev { > > > struct eventfd_ctx *log_ctx; > > > spinlock_t work_lock; > > > struct list_head work_list; > > > - struct task_struct *worker; > > > + int nworkers; > > > + struct task_struct *workers[VHOST_MAX_WORKERS]; > > > }; > > > > > > -long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue > > *vqs, int nvqs); > > > +long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue > > *vqs, int nworkers, int nvqs); > > > long vhost_dev_check_owner(struct vhost_dev *); > > > long vhost_dev_reset_owner(struct vhost_dev *); > > > void vhost_dev_cleanup(struct vhost_dev *); > > > -- > > > 1.7.4.1 > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/20/2012 01:27 PM, Michael S. Tsirkin wrote: > On Mon, Feb 20, 2012 at 09:50:37AM -0600, Tom Lendacky wrote: >> "Michael S. Tsirkin"<mst@redhat.com> wrote on 02/19/2012 08:41:45 AM: >> >>> From: "Michael S. Tsirkin"<mst@redhat.com> >>> To: Anthony Liguori/Austin/IBM@IBMUS >>> Cc: netdev@vger.kernel.org, Tom Lendacky/Austin/IBM@IBMUS, Cristian >>> Viana<vianac@br.ibm.com> >>> Date: 02/19/2012 08:42 AM >>> Subject: Re: [PATCH 1/2] vhost: allow multiple workers threads >>> >>> On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: >>>> This patch allows vhost to have multiple worker threads for devices >> such as >>>> virtio-net which may have multiple virtqueues. >>>> >>>> Since virtqueues are a lockless ring queue, in an ideal world data is >> being >>>> produced by the producer as fast as data is being consumed by the >> consumer. >>>> These loops will continue to consume data until none is left. >>>> >>>> vhost currently multiplexes the consumer side of the queue on a >>> single thread >>>> by attempting to read from the queue until everything is read or it >> cannot >>>> process anymore. This means that activity on one queue may stall >>> another queue. >>> >>> There's actually an attempt to address this: look up >>> VHOST_NET_WEIGHT in the code. I take it, this isn't effective? >>> >>>> This is exacerbated when using any form of polling to read from >>> the queues (as >>>> we'll introduce in the next patch). By spawning a thread per- >>> virtqueue, this >>>> is addressed. >>>> >>>> The only problem with this patch right now is how the wake up of >>> the threads is >>>> done. It's essentially a broadcast and we have seen lock contention as >> a >>>> result. >>> >>> On which lock? >> >> The mutex lock in the vhost_virtqueue struct. This really shows up when >> running with patch 2/2 and increasing the spin_threshold. Both threads wake >> up and try to acquire the mutex. As the spin_threshold increases you end >> up >> with one of the threads getting blocked for a longer and longer time and >> unable to do any RX processing that might be needed. >> >> Tom > > Weird, I had the impression each thread handles one vq. > Isn't this the design? Not the way the code is structured today. There is a single consumer/producer work queue and either the vq notification or other actions may get placed on it. It would be possible to do three threads, one for background tasks and then one for each queue with a more invasive refactoring. But I assumed that the reason the code was structured this was originally was because you saw some value in having a single producer/consumer queue for everything... Regards, Anthony Liguori -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Feb 20, 2012 at 01:46:03PM -0600, Anthony Liguori wrote: > On 02/20/2012 01:27 PM, Michael S. Tsirkin wrote: > >On Mon, Feb 20, 2012 at 09:50:37AM -0600, Tom Lendacky wrote: > >>"Michael S. Tsirkin"<mst@redhat.com> wrote on 02/19/2012 08:41:45 AM: > >> > >>>From: "Michael S. Tsirkin"<mst@redhat.com> > >>>To: Anthony Liguori/Austin/IBM@IBMUS > >>>Cc: netdev@vger.kernel.org, Tom Lendacky/Austin/IBM@IBMUS, Cristian > >>>Viana<vianac@br.ibm.com> > >>>Date: 02/19/2012 08:42 AM > >>>Subject: Re: [PATCH 1/2] vhost: allow multiple workers threads > >>> > >>>On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: > >>>>This patch allows vhost to have multiple worker threads for devices > >>such as > >>>>virtio-net which may have multiple virtqueues. > >>>> > >>>>Since virtqueues are a lockless ring queue, in an ideal world data is > >>being > >>>>produced by the producer as fast as data is being consumed by the > >>consumer. > >>>>These loops will continue to consume data until none is left. > >>>> > >>>>vhost currently multiplexes the consumer side of the queue on a > >>>single thread > >>>>by attempting to read from the queue until everything is read or it > >>cannot > >>>>process anymore. This means that activity on one queue may stall > >>>another queue. > >>> > >>>There's actually an attempt to address this: look up > >>>VHOST_NET_WEIGHT in the code. I take it, this isn't effective? > >>> > >>>>This is exacerbated when using any form of polling to read from > >>>the queues (as > >>>>we'll introduce in the next patch). By spawning a thread per- > >>>virtqueue, this > >>>>is addressed. > >>>> > >>>>The only problem with this patch right now is how the wake up of > >>>the threads is > >>>>done. It's essentially a broadcast and we have seen lock contention as > >>a > >>>>result. > >>> > >>>On which lock? > >> > >>The mutex lock in the vhost_virtqueue struct. This really shows up when > >>running with patch 2/2 and increasing the spin_threshold. Both threads wake > >>up and try to acquire the mutex. As the spin_threshold increases you end > >>up > >>with one of the threads getting blocked for a longer and longer time and > >>unable to do any RX processing that might be needed. > >> > >>Tom > > > >Weird, I had the impression each thread handles one vq. > >Isn't this the design? > > Not the way the code is structured today. There is a single > consumer/producer work queue and either the vq notification or other > actions may get placed on it. And then a random thread picks it up? wont this cause packet reordering? I'll go reread. > It would be possible to do three threads, one for background tasks > and then one for each queue with a more invasive refactoring. > > But I assumed that the reason the code was structured this was > originally was because you saw some value in having a single > producer/consumer queue for everything... > > Regards, > > Anthony Liguori The point was really to avoid scheduler overhead as with tcp, tx and rx tend to run on the same cpu. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2012-02-20 at 23:00 +0200, Michael S. Tsirkin wrote: > > The point was really to avoid scheduler overhead > as with tcp, tx and rx tend to run on the same cpu. We have tried different approaches in the past, like splitting vhost thread to separate TX, RX threads; create per cpu vhost thread instead of creating per VM per virtio_net vhost thread... We think per cpu vhost thread is a better approach based on the data we have collected. It will reduce both vhost resource and scheduler overhead. It will not depend on host scheduler, has less various. The patch is under testing, we hope we can post it soon. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Feb 20, 2012 at 05:04:10PM -0800, Shirley Ma wrote: > On Mon, 2012-02-20 at 23:00 +0200, Michael S. Tsirkin wrote: > > > > The point was really to avoid scheduler overhead > > as with tcp, tx and rx tend to run on the same cpu. > > We have tried different approaches in the past, like splitting vhost > thread to separate TX, RX threads; create per cpu vhost thread instead > of creating per VM per virtio_net vhost thread... > > We think per cpu vhost thread is a better approach based on the data we > have collected. It will reduce both vhost resource and scheduler > overhead. It will not depend on host scheduler, has less various. The > patch is under testing, we hope we can post it soon. > > Thanks > Shirley Yes, great, this is definitely interesting. I actually started with a per-cpu one - it did not perform well but I did not figure out why, switching to a single thread fixed it and I did not dig into it.
On Tue, 2012-02-21 at 05:21 +0200, Michael S. Tsirkin wrote: > On Mon, Feb 20, 2012 at 05:04:10PM -0800, Shirley Ma wrote: > > On Mon, 2012-02-20 at 23:00 +0200, Michael S. Tsirkin wrote: > > > > > > The point was really to avoid scheduler overhead > > > as with tcp, tx and rx tend to run on the same cpu. > > > > We have tried different approaches in the past, like splitting vhost > > thread to separate TX, RX threads; create per cpu vhost thread > instead > > of creating per VM per virtio_net vhost thread... > > > > We think per cpu vhost thread is a better approach based on the data > we > > have collected. It will reduce both vhost resource and scheduler > > overhead. It will not depend on host scheduler, has less various. > The > > patch is under testing, we hope we can post it soon. > > > > Thanks > > Shirley > > Yes, great, this is definitely interesting. I actually started with > a per-cpu one - it did not perform well but I did not > figure out why, switching to a single thread fixed it > and I did not dig into it. The patch includes per cpu vhost thread & vhost NUMA aware scheduling It is very interesting. We are collecting performance data with different workloads (streams, request/response) related to which VCPU runs on which CPU, which vhost cpu thread is being scheduled, and which NIC TX/RX queues is being used. The performance were different when using different vhost scheduling approach for both TX/RX worker. The results seems pretty good: like 60 UDP_RRs, the results event more than doubled in our lab. However the TCP_RRs results couldn't catch up UDP_RRs. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/21/2012 03:46 AM, Anthony Liguori wrote: > On 02/20/2012 01:27 PM, Michael S. Tsirkin wrote: >> On Mon, Feb 20, 2012 at 09:50:37AM -0600, Tom Lendacky wrote: >>> "Michael S. Tsirkin"<mst@redhat.com> wrote on 02/19/2012 08:41:45 AM: >>> >>>> From: "Michael S. Tsirkin"<mst@redhat.com> >>>> To: Anthony Liguori/Austin/IBM@IBMUS >>>> Cc: netdev@vger.kernel.org, Tom Lendacky/Austin/IBM@IBMUS, Cristian >>>> Viana<vianac@br.ibm.com> >>>> Date: 02/19/2012 08:42 AM >>>> Subject: Re: [PATCH 1/2] vhost: allow multiple workers threads >>>> >>>> On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: >>>>> This patch allows vhost to have multiple worker threads for devices >>> such as >>>>> virtio-net which may have multiple virtqueues. >>>>> >>>>> Since virtqueues are a lockless ring queue, in an ideal world data is >>> being >>>>> produced by the producer as fast as data is being consumed by the >>> consumer. >>>>> These loops will continue to consume data until none is left. >>>>> >>>>> vhost currently multiplexes the consumer side of the queue on a >>>> single thread >>>>> by attempting to read from the queue until everything is read or it >>> cannot >>>>> process anymore. This means that activity on one queue may stall >>>> another queue. >>>> >>>> There's actually an attempt to address this: look up >>>> VHOST_NET_WEIGHT in the code. I take it, this isn't effective? >>>> >>>>> This is exacerbated when using any form of polling to read from >>>> the queues (as >>>>> we'll introduce in the next patch). By spawning a thread per- >>>> virtqueue, this >>>>> is addressed. >>>>> >>>>> The only problem with this patch right now is how the wake up of >>>> the threads is >>>>> done. It's essentially a broadcast and we have seen lock >>>>> contention as >>> a >>>>> result. >>>> >>>> On which lock? >>> >>> The mutex lock in the vhost_virtqueue struct. This really shows up >>> when >>> running with patch 2/2 and increasing the spin_threshold. Both >>> threads wake >>> up and try to acquire the mutex. As the spin_threshold increases >>> you end >>> up >>> with one of the threads getting blocked for a longer and longer time >>> and >>> unable to do any RX processing that might be needed. >>> >>> Tom >> >> Weird, I had the impression each thread handles one vq. >> Isn't this the design? > > Not the way the code is structured today. There is a single > consumer/producer work queue and either the vq notification or other > actions may get placed on it. > > It would be possible to do three threads, one for background tasks and > then one for each queue with a more invasive refactoring. > > But I assumed that the reason the code was structured this was > originally was because you saw some value in having a single > producer/consumer queue for everything... > > Regards, > > Anthony Liguori Not sure I'm reading the code correctly, looks like with this series, two worker threads can try to handle the work of a same virtqueue? Looks strange as the notification from other side (guest/net) should be disabled even if vhost thread is spinning. > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/19/2012 10:41 PM, Michael S. Tsirkin wrote: > On Fri, Feb 17, 2012 at 05:02:05PM -0600, Anthony Liguori wrote: >> > This patch allows vhost to have multiple worker threads for devices such as >> > virtio-net which may have multiple virtqueues. >> > >> > Since virtqueues are a lockless ring queue, in an ideal world data is being >> > produced by the producer as fast as data is being consumed by the consumer. >> > These loops will continue to consume data until none is left. >> > >> > vhost currently multiplexes the consumer side of the queue on a single thread >> > by attempting to read from the queue until everything is read or it cannot >> > process anymore. This means that activity on one queue may stall another queue. > There's actually an attempt to address this: look up > VHOST_NET_WEIGHT in the code. I take it, this isn't effective? > >> > This is exacerbated when using any form of polling to read from the queues (as >> > we'll introduce in the next patch). By spawning a thread per-virtqueue, this >> > is addressed. >> > >> > The only problem with this patch right now is how the wake up of the threads is >> > done. It's essentially a broadcast and we have seen lock contention as a >> > result. > On which lock? > >> > We've tried some approaches to signal a single thread but I'm not >> > confident that that code is correct yet so I'm only sending the broadcast >> > version. > Yes, that looks like an obvious question. > >> > Here are some performance results from this change. There's a modest >> > improvement with stream although a fair bit of variability too. >> > >> > With RR, there's pretty significant improvements as the instance rate drives up. > Interesting. This was actually tested at one time and we saw > a significant performance improvement from using > a single thread especially with a single > stream in the guest. Profiling indicated that > with a single thread we get too many context > switches between TX and RX, since guest networking > tends to run TX and RX processing on the same > guest VCPU. > > Maybe we were wrong or maybe this went away > for some reason. I'll see if this can be reproduced. > I've tried a similar test in Jan. The test uses one dedicated vhost thread to handle tx requests and another one for rx. Test result shows much degradation as the both of the #exits and #irq are increased. There are some differences as I test between local host and guest, and the guest does not have very recent virtio changes ( unlocked kick and exposing index immediately ). I would try the recent kernel. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/20/2012 10:03 PM, Shirley Ma wrote: > On Tue, 2012-02-21 at 05:21 +0200, Michael S. Tsirkin wrote: >> On Mon, Feb 20, 2012 at 05:04:10PM -0800, Shirley Ma wrote: >>> On Mon, 2012-02-20 at 23:00 +0200, Michael S. Tsirkin wrote: >>>> >>>> The point was really to avoid scheduler overhead >>>> as with tcp, tx and rx tend to run on the same cpu. >>> >>> We have tried different approaches in the past, like splitting vhost >>> thread to separate TX, RX threads; create per cpu vhost thread >> instead >>> of creating per VM per virtio_net vhost thread... >>> >>> We think per cpu vhost thread is a better approach based on the data >> we >>> have collected. It will reduce both vhost resource and scheduler >>> overhead. It will not depend on host scheduler, has less various. >> The >>> patch is under testing, we hope we can post it soon. >>> >>> Thanks >>> Shirley >> >> Yes, great, this is definitely interesting. I actually started with >> a per-cpu one - it did not perform well but I did not >> figure out why, switching to a single thread fixed it >> and I did not dig into it. > > The patch includes per cpu vhost thread& vhost NUMA aware scheduling Hi Shirley, Are you planning on posting these patches soon? Regards, Anthony Liguori -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2012-03-05 at 07:21 -0600, Anthony Liguori wrote: > Hi Shirley, > > Are you planning on posting these patches soon? > > Regards, > > Anthony Liguori I thought to compare with different scheduling with different NICs before submitting it. Maybe it's better to submit a RFC patch to get review comments now. Let me clean up the patch and submit it here. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 9dab1f5..47175cd 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -33,6 +33,10 @@ static int experimental_zcopytx; module_param(experimental_zcopytx, int, 0444); MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX"); +static int workers = 2; +module_param(workers, int, 0444); +MODULE_PARM_DESC(workers, "Set the number of worker threads"); + /* Max number of bytes transferred before requeueing the job. * Using this limit prevents one virtqueue from starving others. */ #define VHOST_NET_WEIGHT 0x80000 @@ -504,7 +508,7 @@ static int vhost_net_open(struct inode *inode, struct file *f) dev = &n->dev; n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick; n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick; - r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX); + r = vhost_dev_init(dev, n->vqs, workers, VHOST_NET_VQ_MAX); if (r < 0) { kfree(n); return r; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c14c42b..676cead 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -144,9 +144,12 @@ static inline void vhost_work_queue(struct vhost_dev *dev, spin_lock_irqsave(&dev->work_lock, flags); if (list_empty(&work->node)) { + int i; + list_add_tail(&work->node, &dev->work_list); work->queue_seq++; - wake_up_process(dev->worker); + for (i = 0; i < dev->nworkers; i++) + wake_up_process(dev->workers[i]); } spin_unlock_irqrestore(&dev->work_lock, flags); } @@ -287,7 +290,7 @@ static void vhost_dev_free_iovecs(struct vhost_dev *dev) } long vhost_dev_init(struct vhost_dev *dev, - struct vhost_virtqueue *vqs, int nvqs) + struct vhost_virtqueue *vqs, int nworkers, int nvqs) { int i; @@ -300,7 +303,9 @@ long vhost_dev_init(struct vhost_dev *dev, dev->mm = NULL; spin_lock_init(&dev->work_lock); INIT_LIST_HEAD(&dev->work_list); - dev->worker = NULL; + dev->nworkers = min(nworkers, VHOST_MAX_WORKERS); + for (i = 0; i < dev->nworkers; i++) + dev->workers[i] = NULL; for (i = 0; i < dev->nvqs; ++i) { dev->vqs[i].log = NULL; @@ -354,7 +359,7 @@ static int vhost_attach_cgroups(struct vhost_dev *dev) static long vhost_dev_set_owner(struct vhost_dev *dev) { struct task_struct *worker; - int err; + int err, i; /* Is there an owner already? */ if (dev->mm) { @@ -364,28 +369,34 @@ static long vhost_dev_set_owner(struct vhost_dev *dev) /* No owner, become one */ dev->mm = get_task_mm(current); - worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid); - if (IS_ERR(worker)) { - err = PTR_ERR(worker); - goto err_worker; - } + for (i = 0; i < dev->nworkers; i++) { + worker = kthread_create(vhost_worker, dev, "vhost-%d.%d", current->pid, i); + if (IS_ERR(worker)) { + err = PTR_ERR(worker); + goto err_worker; + } - dev->worker = worker; - wake_up_process(worker); /* avoid contributing to loadavg */ + dev->workers[i] = worker; + wake_up_process(worker); /* avoid contributing to loadavg */ + } err = vhost_attach_cgroups(dev); if (err) - goto err_cgroup; + goto err_worker; err = vhost_dev_alloc_iovecs(dev); if (err) - goto err_cgroup; + goto err_worker; return 0; -err_cgroup: - kthread_stop(worker); - dev->worker = NULL; + err_worker: + for (i = 0; i < dev->nworkers; i++) { + if (dev->workers[i]) { + kthread_stop(dev->workers[i]); + dev->workers[i] = NULL; + } + } if (dev->mm) mmput(dev->mm); dev->mm = NULL; @@ -475,9 +486,11 @@ void vhost_dev_cleanup(struct vhost_dev *dev) lockdep_is_held(&dev->mutex))); RCU_INIT_POINTER(dev->memory, NULL); WARN_ON(!list_empty(&dev->work_list)); - if (dev->worker) { - kthread_stop(dev->worker); - dev->worker = NULL; + for (i = 0; i < dev->nworkers; i++) { + if (dev->workers[i]) { + kthread_stop(dev->workers[i]); + dev->workers[i] = NULL; + } } if (dev->mm) mmput(dev->mm); diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index a801e28..fa5e75e 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -18,6 +18,9 @@ #define VHOST_DMA_DONE_LEN 1 #define VHOST_DMA_CLEAR_LEN 0 +/* Maximum number of worker threads per-vhost device */ +#define VHOST_MAX_WORKERS 8 + struct vhost_device; struct vhost_work; @@ -157,10 +160,11 @@ struct vhost_dev { struct eventfd_ctx *log_ctx; spinlock_t work_lock; struct list_head work_list; - struct task_struct *worker; + int nworkers; + struct task_struct *workers[VHOST_MAX_WORKERS]; }; -long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs); +long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nworkers, int nvqs); long vhost_dev_check_owner(struct vhost_dev *); long vhost_dev_reset_owner(struct vhost_dev *); void vhost_dev_cleanup(struct vhost_dev *);
This patch allows vhost to have multiple worker threads for devices such as virtio-net which may have multiple virtqueues. Since virtqueues are a lockless ring queue, in an ideal world data is being produced by the producer as fast as data is being consumed by the consumer. These loops will continue to consume data until none is left. vhost currently multiplexes the consumer side of the queue on a single thread by attempting to read from the queue until everything is read or it cannot process anymore. This means that activity on one queue may stall another queue. This is exacerbated when using any form of polling to read from the queues (as we'll introduce in the next patch). By spawning a thread per-virtqueue, this is addressed. The only problem with this patch right now is how the wake up of the threads is done. It's essentially a broadcast and we have seen lock contention as a result. We've tried some approaches to signal a single thread but I'm not confident that that code is correct yet so I'm only sending the broadcast version. Here are some performance results from this change. There's a modest improvement with stream although a fair bit of variability too. With RR, there's pretty significant improvements as the instance rate drives up. Test, Size, Instance, Baseline, Patch, Relative TCP_RR Tx:256 Rx:256 1 9,639.66 10,164.06 105.44% 10 62,819.55 54,059.78 86.06% 30 84,715.60 131,241.86 154.92% 60 124,614.71 148,720.66 119.34% UDP_RR Tx:256 Rx:256 1 9,652.50 10,343.72 107.16% 10 53,830.26 58,235.90 108.18% 30 89,471.01 97,634.53 109.12% 60 103,640.59 164,035.01 158.27% TCP_STREAM Tx: 256 1 2,622.63 2,610.71 99.55% 4 4,928.02 4,812.05 97.65% Tx: 1024 1 5,639.89 5,751.28 101.97% 4 5,874.72 6,575.55 111.93% Tx: 4096 1 6,257.42 7,655.22 122.34% 4 5,370.78 6,044.83 112.55% Tx: 16384 1 6,346.63 7,267.44 114.51% 4 5,198.02 5,657.12 108.83% TCP_MAERTS Rx: 256 1 2,091.38 1,765.62 84.42% 4 5,319.52 5,619.49 105.64% Rx: 1024 1 7,030.66 7,593.61 108.01% 4 9,040.53 7,275.84 80.48% Rx: 4096 1 9,160.93 9,318.15 101.72% 4 9,372.49 8,875.63 94.70% Rx: 16384 1 9,183.28 9,134.02 99.46% 4 9,377.17 8,877.52 94.67% 106.46% Cc: Tom Lendacky <toml@us.ibm.com> Cc: Cristian Viana <vianac@br.ibm.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> --- drivers/vhost/net.c | 6 ++++- drivers/vhost/vhost.c | 51 ++++++++++++++++++++++++++++++------------------ drivers/vhost/vhost.h | 8 +++++- 3 files changed, 43 insertions(+), 22 deletions(-)