| Message ID | 1506067355-5771-4-git-send-email-jasowang@redhat.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | batched tx processing in vhost_net | expand |
On Fri, Sep 22, 2017 at 04:02:33PM +0800, Jason Wang wrote: > This patch introduces a helper which just increase the used idx. This > will be used in pair with vhost_prefetch_desc_indices() by batching > code. > > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ > drivers/vhost/vhost.h | 1 + > 2 files changed, 34 insertions(+) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
On Fri, Sep 22, 2017 at 04:02:33PM +0800, Jason Wang wrote: > This patch introduces a helper which just increase the used idx. This > will be used in pair with vhost_prefetch_desc_indices() by batching > code. > > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ > drivers/vhost/vhost.h | 1 + > 2 files changed, 34 insertions(+) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 8424166d..6532cda 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2178,6 +2178,39 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) > } > EXPORT_SYMBOL_GPL(vhost_add_used); > > +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n) > +{ > + u16 old, new; > + > + old = vq->last_used_idx; > + new = (vq->last_used_idx += n); > + /* If the driver never bothers to signal in a very long while, > + * used index might wrap around. If that happens, invalidate > + * signalled_used index we stored. TODO: make sure driver > + * signals at least once in 2^16 and remove this. > + */ > + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) > + vq->signalled_used_valid = false; > + > + /* Make sure buffer is written before we update index. */ > + smp_wmb(); > + if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx), > + &vq->used->idx)) { > + vq_err(vq, "Failed to increment used idx"); > + return -EFAULT; > + } > + if (unlikely(vq->log_used)) { > + /* Log used index update. */ > + log_write(vq->log_base, > + vq->log_addr + offsetof(struct vring_used, idx), > + sizeof(vq->used->idx)); > + if (vq->log_ctx) > + eventfd_signal(vq->log_ctx, 1); > + } > + return 0; > +} > +EXPORT_SYMBOL_GPL(vhost_add_used_idx); > + > static int __vhost_add_used_n(struct vhost_virtqueue *vq, > struct vring_used_elem *heads, > unsigned count) > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index 16c2cb6..5dd6c05 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, > void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); > > int vhost_vq_init_access(struct vhost_virtqueue *); > +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); > int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); > int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, > unsigned count); Please change the API to hide the fact that there's an index that needs to be updated. > -- > 2.7.4
On 2017年09月27日 03:13, Michael S. Tsirkin wrote: > On Fri, Sep 22, 2017 at 04:02:33PM +0800, Jason Wang wrote: >> This patch introduces a helper which just increase the used idx. This >> will be used in pair with vhost_prefetch_desc_indices() by batching >> code. >> >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ >> drivers/vhost/vhost.h | 1 + >> 2 files changed, 34 insertions(+) >> >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >> index 8424166d..6532cda 100644 >> --- a/drivers/vhost/vhost.c >> +++ b/drivers/vhost/vhost.c >> @@ -2178,6 +2178,39 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) >> } >> EXPORT_SYMBOL_GPL(vhost_add_used); >> >> +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n) >> +{ >> + u16 old, new; >> + >> + old = vq->last_used_idx; >> + new = (vq->last_used_idx += n); >> + /* If the driver never bothers to signal in a very long while, >> + * used index might wrap around. If that happens, invalidate >> + * signalled_used index we stored. TODO: make sure driver >> + * signals at least once in 2^16 and remove this. >> + */ >> + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) >> + vq->signalled_used_valid = false; >> + >> + /* Make sure buffer is written before we update index. */ >> + smp_wmb(); >> + if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx), >> + &vq->used->idx)) { >> + vq_err(vq, "Failed to increment used idx"); >> + return -EFAULT; >> + } >> + if (unlikely(vq->log_used)) { >> + /* Log used index update. */ >> + log_write(vq->log_base, >> + vq->log_addr + offsetof(struct vring_used, idx), >> + sizeof(vq->used->idx)); >> + if (vq->log_ctx) >> + eventfd_signal(vq->log_ctx, 1); >> + } >> + return 0; >> +} >> +EXPORT_SYMBOL_GPL(vhost_add_used_idx); >> + >> static int __vhost_add_used_n(struct vhost_virtqueue *vq, >> struct vring_used_elem *heads, >> unsigned count) >> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h >> index 16c2cb6..5dd6c05 100644 >> --- a/drivers/vhost/vhost.h >> +++ b/drivers/vhost/vhost.h >> @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, >> void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); >> >> int vhost_vq_init_access(struct vhost_virtqueue *); >> +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); >> int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); >> int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, >> unsigned count); > Please change the API to hide the fact that there's an index that needs > to be updated. In fact, an interesting optimization on top is just call vhost_add_used_idx(vq, n) instead of n vhost_add_used_idx(vq, 1). That's the reason I leave n in the API. Thanks > >> -- >> 2.7.4
On Wed, Sep 27, 2017 at 08:38:24AM +0800, Jason Wang wrote: > > > On 2017年09月27日 03:13, Michael S. Tsirkin wrote: > > On Fri, Sep 22, 2017 at 04:02:33PM +0800, Jason Wang wrote: > > > This patch introduces a helper which just increase the used idx. This > > > will be used in pair with vhost_prefetch_desc_indices() by batching > > > code. > > > > > > Signed-off-by: Jason Wang <jasowang@redhat.com> > > > --- > > > drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ > > > drivers/vhost/vhost.h | 1 + > > > 2 files changed, 34 insertions(+) > > > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index 8424166d..6532cda 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -2178,6 +2178,39 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) > > > } > > > EXPORT_SYMBOL_GPL(vhost_add_used); > > > +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n) > > > +{ > > > + u16 old, new; > > > + > > > + old = vq->last_used_idx; > > > + new = (vq->last_used_idx += n); > > > + /* If the driver never bothers to signal in a very long while, > > > + * used index might wrap around. If that happens, invalidate > > > + * signalled_used index we stored. TODO: make sure driver > > > + * signals at least once in 2^16 and remove this. > > > + */ > > > + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) > > > + vq->signalled_used_valid = false; > > > + > > > + /* Make sure buffer is written before we update index. */ > > > + smp_wmb(); > > > + if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx), > > > + &vq->used->idx)) { > > > + vq_err(vq, "Failed to increment used idx"); > > > + return -EFAULT; > > > + } > > > + if (unlikely(vq->log_used)) { > > > + /* Log used index update. */ > > > + log_write(vq->log_base, > > > + vq->log_addr + offsetof(struct vring_used, idx), > > > + sizeof(vq->used->idx)); > > > + if (vq->log_ctx) > > > + eventfd_signal(vq->log_ctx, 1); > > > + } > > > + return 0; > > > +} > > > +EXPORT_SYMBOL_GPL(vhost_add_used_idx); > > > + > > > static int __vhost_add_used_n(struct vhost_virtqueue *vq, > > > struct vring_used_elem *heads, > > > unsigned count) > > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > > index 16c2cb6..5dd6c05 100644 > > > --- a/drivers/vhost/vhost.h > > > +++ b/drivers/vhost/vhost.h > > > @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, > > > void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); > > > int vhost_vq_init_access(struct vhost_virtqueue *); > > > +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); > > > int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); > > > int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, > > > unsigned count); > > Please change the API to hide the fact that there's an index that needs > > to be updated. > > In fact, an interesting optimization on top is just call > vhost_add_used_idx(vq, n) instead of n vhost_add_used_idx(vq, 1). That's the > reason I leave n in the API. > > Thanks Right but you could increment some internal counter in the vq structure then update the used index using some api with a generic name, e.g. add_used_complete or something like this. > > > > > -- > > > 2.7.4
>> > > @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, >> > > void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); >> > > int vhost_vq_init_access(struct vhost_virtqueue *); >> > > +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); >> > > int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); >> > > int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, >> > > unsigned count); >> > Please change the API to hide the fact that there's an index that needs >> > to be updated. >> >> In fact, an interesting optimization on top is just call >> vhost_add_used_idx(vq, n) instead of n vhost_add_used_idx(vq, 1). That's the >> reason I leave n in the API. >> >> Thanks > > Right but you could increment some internal counter in the vq > structure then update the used index using some api > with a generic name, e.g. add_used_complete or something like this. That adds a layer of information hiding. If the same variable can be kept close to the computation in a local variable and passed directly to vhost_add_used_idx_n that is easier to follow.
On 2017年09月28日 06:58, Michael S. Tsirkin wrote: > On Wed, Sep 27, 2017 at 08:38:24AM +0800, Jason Wang wrote: >> On 2017年09月27日 03:13, Michael S. Tsirkin wrote: >>> On Fri, Sep 22, 2017 at 04:02:33PM +0800, Jason Wang wrote: >>>> This patch introduces a helper which just increase the used idx. This >>>> will be used in pair with vhost_prefetch_desc_indices() by batching >>>> code. >>>> >>>> Signed-off-by: Jason Wang<jasowang@redhat.com> >>>> --- >>>> drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ >>>> drivers/vhost/vhost.h | 1 + >>>> 2 files changed, 34 insertions(+) >>>> >>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >>>> index 8424166d..6532cda 100644 >>>> --- a/drivers/vhost/vhost.c >>>> +++ b/drivers/vhost/vhost.c >>>> @@ -2178,6 +2178,39 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) >>>> } >>>> EXPORT_SYMBOL_GPL(vhost_add_used); >>>> +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n) >>>> +{ >>>> + u16 old, new; >>>> + >>>> + old = vq->last_used_idx; >>>> + new = (vq->last_used_idx += n); >>>> + /* If the driver never bothers to signal in a very long while, >>>> + * used index might wrap around. If that happens, invalidate >>>> + * signalled_used index we stored. TODO: make sure driver >>>> + * signals at least once in 2^16 and remove this. >>>> + */ >>>> + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) >>>> + vq->signalled_used_valid = false; >>>> + >>>> + /* Make sure buffer is written before we update index. */ >>>> + smp_wmb(); >>>> + if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx), >>>> + &vq->used->idx)) { >>>> + vq_err(vq, "Failed to increment used idx"); >>>> + return -EFAULT; >>>> + } >>>> + if (unlikely(vq->log_used)) { >>>> + /* Log used index update. */ >>>> + log_write(vq->log_base, >>>> + vq->log_addr + offsetof(struct vring_used, idx), >>>> + sizeof(vq->used->idx)); >>>> + if (vq->log_ctx) >>>> + eventfd_signal(vq->log_ctx, 1); >>>> + } >>>> + return 0; >>>> +} >>>> +EXPORT_SYMBOL_GPL(vhost_add_used_idx); >>>> + >>>> static int __vhost_add_used_n(struct vhost_virtqueue *vq, >>>> struct vring_used_elem *heads, >>>> unsigned count) >>>> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h >>>> index 16c2cb6..5dd6c05 100644 >>>> --- a/drivers/vhost/vhost.h >>>> +++ b/drivers/vhost/vhost.h >>>> @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, >>>> void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); >>>> int vhost_vq_init_access(struct vhost_virtqueue *); >>>> +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); >>>> int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); >>>> int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, >>>> unsigned count); >>> Please change the API to hide the fact that there's an index that needs >>> to be updated. >> In fact, an interesting optimization on top is just call >> vhost_add_used_idx(vq, n) instead of n vhost_add_used_idx(vq, 1). That's the >> reason I leave n in the API. >> >> Thanks > Right but you could increment some internal counter in the vq > structure then update the used index using some api > with a generic name, e.g. add_used_complete or something like this. > Right, I see. Thanks
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 8424166d..6532cda 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2178,6 +2178,39 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) } EXPORT_SYMBOL_GPL(vhost_add_used); +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n) +{ + u16 old, new; + + old = vq->last_used_idx; + new = (vq->last_used_idx += n); + /* If the driver never bothers to signal in a very long while, + * used index might wrap around. If that happens, invalidate + * signalled_used index we stored. TODO: make sure driver + * signals at least once in 2^16 and remove this. + */ + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) + vq->signalled_used_valid = false; + + /* Make sure buffer is written before we update index. */ + smp_wmb(); + if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx), + &vq->used->idx)) { + vq_err(vq, "Failed to increment used idx"); + return -EFAULT; + } + if (unlikely(vq->log_used)) { + /* Log used index update. */ + log_write(vq->log_base, + vq->log_addr + offsetof(struct vring_used, idx), + sizeof(vq->used->idx)); + if (vq->log_ctx) + eventfd_signal(vq->log_ctx, 1); + } + return 0; +} +EXPORT_SYMBOL_GPL(vhost_add_used_idx); + static int __vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads, unsigned count) diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index 16c2cb6..5dd6c05 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -199,6 +199,7 @@ int __vhost_get_vq_desc(struct vhost_virtqueue *vq, void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); int vhost_vq_init_access(struct vhost_virtqueue *); +int vhost_add_used_idx(struct vhost_virtqueue *vq, int n); int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len); int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads, unsigned count);
This patch introduces a helper which just increase the used idx. This will be used in pair with vhost_prefetch_desc_indices() by batching code. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++ drivers/vhost/vhost.h | 1 + 2 files changed, 34 insertions(+)