| Message ID | 41be791c0911091004x62d30fbey91ef730475ba3571@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
Saul Tamari wrote: > This patch reduces the size of memory being cleared on every virtio-blk IO. > > Improve number of IOPS when using avirtio-blk device. > > On every virtio-blk IO command passed to QEMU, virtio_blk_alloc_request() > allocates and clears (with qemu_mallocz()) a VirtIOBlockReq object. > The sizeof(VirtIOBlockReq) equals 41040 bytes on my x86-64 machine. > By moving the 'elem' variable to the end of VirtIOBlockReq and > clearing only upto the address of the 'elem.in_addr' field, the > memset() call now clears only 80 bytes. > > > Signed-off-by: Saul Tamari <stamari@gmail.com> > --- > > diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c > index 2630b99..de74b00 100644 > --- a/hw/virtio-blk.c > +++ b/hw/virtio-blk.c > @@ -79,12 +79,13 @@ static inline void virtio_identify_template(struct > virtio_blk_config *bc) > This patch is whitespace damaged by your mailer. Regards, Anthony Liguori
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c index 2630b99..de74b00 100644 --- a/hw/virtio-blk.c +++ b/hw/virtio-blk.c @@ -79,12 +79,13 @@ static inline void virtio_identify_template(struct virtio_blk_config *bc) typedef struct VirtIOBlockReq { VirtIOBlock *dev; - VirtQueueElement elem; struct virtio_blk_inhdr *in; struct virtio_blk_outhdr *out; struct virtio_scsi_inhdr *scsi; QEMUIOVector qiov; struct VirtIOBlockReq *next; + /* Members that need clearing, must be added prior to elem */ + VirtQueueElement elem; } VirtIOBlockReq;
This patch reduces the size of memory being cleared on every virtio-blk IO. Improve number of IOPS when using avirtio-blk device. On every virtio-blk IO command passed to QEMU, virtio_blk_alloc_request() allocates and clears (with qemu_mallocz()) a VirtIOBlockReq object. The sizeof(VirtIOBlockReq) equals 41040 bytes on my x86-64 machine. By moving the 'elem' variable to the end of VirtIOBlockReq and clearing only upto the address of the 'elem.in_addr' field, the memset() call now clears only 80 bytes. Signed-off-by: Saul Tamari <stamari@gmail.com> --- static void virtio_blk_req_complete(VirtIOBlockReq *req, int status) @@ -139,7 +140,8 @@ static void virtio_blk_flush_complete(void *opaque, int ret) static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s) { - VirtIOBlockReq *req = qemu_mallocz(sizeof(*req)); + VirtIOBlockReq *req = qemu_malloc(sizeof(*req)); + memset(req, 0, offsetof(VirtIOBlockReq, elem.in_addr[0])); req->dev = s; return req; }