* [PATCH] virtio-blk: Disable callback in virtblk_done() @ 2012-09-25 2:36 Asias He 2012-09-25 14:08 ` Asias He 0 siblings, 1 reply; 9+ messages in thread From: Asias He @ 2012-09-25 2:36 UTC (permalink / raw) To: Rusty Russell; +Cc: virtualization, kvm, Michael S. Tsirkin This reduces unnecessary interrupts that host could send to guest while guest is in the progress of irq handling. If one vcpu is handling the irq, while another interrupt comes, in handle_edge_irq(), the guest will mask the interrupt via mask_msi_irq() which is a very heavy operation that goes all the way down to host. Signed-off-by: Asias He <asias@redhat.com> --- drivers/block/virtio_blk.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 53b81d5..0bdde8f 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -274,15 +274,18 @@ static void virtblk_done(struct virtqueue *vq) unsigned int len; spin_lock_irqsave(vblk->disk->queue->queue_lock, flags); - while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { - if (vbr->bio) { - virtblk_bio_done(vbr); - bio_done = true; - } else { - virtblk_request_done(vbr); - req_done = true; + do { + virtqueue_disable_cb(vq); + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { + if (vbr->bio) { + virtblk_bio_done(vbr); + bio_done = true; + } else { + virtblk_request_done(vbr); + req_done = true; + } } - } + } while (!virtqueue_enable_cb(vq)); /* In case queue is stopped waiting for more buffers. */ if (req_done) blk_start_queue(vblk->disk->queue); -- 1.7.11.4 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-25 2:36 [PATCH] virtio-blk: Disable callback in virtblk_done() Asias He @ 2012-09-25 14:08 ` Asias He 2012-09-27 0:10 ` Rusty Russell 0 siblings, 1 reply; 9+ messages in thread From: Asias He @ 2012-09-25 14:08 UTC (permalink / raw) To: Rusty Russell; +Cc: virtualization, kvm, Michael S. Tsirkin On 09/25/2012 10:36 AM, Asias He wrote: > This reduces unnecessary interrupts that host could send to guest while > guest is in the progress of irq handling. > > If one vcpu is handling the irq, while another interrupt comes, in > handle_edge_irq(), the guest will mask the interrupt via mask_msi_irq() > which is a very heavy operation that goes all the way down to host. > > Signed-off-by: Asias He <asias@redhat.com> > --- Here are some performance numbers on qemu: Before: ------------------------------------- seq-read : io=0 B, bw=269730KB/s, iops=67432 , runt= 62200msec seq-write : io=0 B, bw=339716KB/s, iops=84929 , runt= 49386msec rand-read : io=0 B, bw=270435KB/s, iops=67608 , runt= 62038msec rand-write: io=0 B, bw=354436KB/s, iops=88608 , runt= 47335msec clat (usec): min=101 , max=138052 , avg=14822.09, stdev=11771.01 clat (usec): min=96 , max=81543 , avg=11798.94, stdev=7735.60 clat (usec): min=128 , max=140043 , avg=14835.85, stdev=11765.33 clat (usec): min=109 , max=147207 , avg=11337.09, stdev=5990.35 cpu : usr=15.93%, sys=60.37%, ctx=7764972, majf=0, minf=54 cpu : usr=32.73%, sys=120.49%, ctx=7372945, majf=0, minf=1 cpu : usr=18.84%, sys=58.18%, ctx=7775420, majf=0, minf=1 cpu : usr=24.20%, sys=59.85%, ctx=8307886, majf=0, minf=0 vdb: ios=8389107/8368136, merge=0/0, ticks=19457874/14616506, in_queue=34206098, util=99.68% 43: interrupt in total: 887320 fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 --filename=/dev/vdb --name=seq-read --stonewall --rw=read --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall --rw=randread --name=rnd-write --stonewall --rw=randwrite After: ------------------------------------- seq-read : io=0 B, bw=309503KB/s, iops=77375 , runt= 54207msec seq-write : io=0 B, bw=448205KB/s, iops=112051 , runt= 37432msec rand-read : io=0 B, bw=311254KB/s, iops=77813 , runt= 53902msec rand-write: io=0 B, bw=377152KB/s, iops=94287 , runt= 44484msec clat (usec): min=81 , max=90588 , avg=12946.06, stdev=9085.94 clat (usec): min=57 , max=72264 , avg=8967.97, stdev=5951.04 clat (usec): min=29 , max=101046 , avg=12889.95, stdev=9067.91 clat (usec): min=52 , max=106152 , avg=10660.56, stdev=4778.19 cpu : usr=15.05%, sys=57.92%, ctx=7710941, majf=0, minf=54 cpu : usr=26.78%, sys=101.40%, ctx=7387891, majf=0, minf=2 cpu : usr=19.03%, sys=58.17%, ctx=7681976, majf=0, minf=8 cpu : usr=24.65%, sys=58.34%, ctx=8442632, majf=0, minf=4 vdb: ios=8389086/8361888, merge=0/0, ticks=17243780/12742010, in_queue=30078377, util=99.59% 43: interrupt in total: 1259639 fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 --filename=/dev/vdb --name=seq-read --stonewall --rw=read --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall --rw=randread --name=rnd-write --stonewall --rw=randwrite > drivers/block/virtio_blk.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 53b81d5..0bdde8f 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -274,15 +274,18 @@ static void virtblk_done(struct virtqueue *vq) > unsigned int len; > > spin_lock_irqsave(vblk->disk->queue->queue_lock, flags); > - while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { > - if (vbr->bio) { > - virtblk_bio_done(vbr); > - bio_done = true; > - } else { > - virtblk_request_done(vbr); > - req_done = true; > + do { > + virtqueue_disable_cb(vq); > + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { > + if (vbr->bio) { > + virtblk_bio_done(vbr); > + bio_done = true; > + } else { > + virtblk_request_done(vbr); > + req_done = true; > + } > } > - } > + } while (!virtqueue_enable_cb(vq)); > /* In case queue is stopped waiting for more buffers. */ > if (req_done) > blk_start_queue(vblk->disk->queue); > -- Asias ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-25 14:08 ` Asias He @ 2012-09-27 0:10 ` Rusty Russell 2012-09-27 6:48 ` Asias He ` (3 more replies) 0 siblings, 4 replies; 9+ messages in thread From: Rusty Russell @ 2012-09-27 0:10 UTC (permalink / raw) To: Asias He; +Cc: virtualization, kvm, Michael S. Tsirkin Asias He <asias@redhat.com> writes: > On 09/25/2012 10:36 AM, Asias He wrote: >> This reduces unnecessary interrupts that host could send to guest while >> guest is in the progress of irq handling. >> >> If one vcpu is handling the irq, while another interrupt comes, in >> handle_edge_irq(), the guest will mask the interrupt via mask_msi_irq() >> which is a very heavy operation that goes all the way down to host. >> >> Signed-off-by: Asias He <asias@redhat.com> >> --- > > Here are some performance numbers on qemu: I assume this is with qemu using kvm, not qemu in soft emulation? :) > Before: > ------------------------------------- > seq-read : io=0 B, bw=269730KB/s, iops=67432 , runt= 62200msec > seq-write : io=0 B, bw=339716KB/s, iops=84929 , runt= 49386msec > rand-read : io=0 B, bw=270435KB/s, iops=67608 , runt= 62038msec > rand-write: io=0 B, bw=354436KB/s, iops=88608 , runt= 47335msec > clat (usec): min=101 , max=138052 , avg=14822.09, stdev=11771.01 > clat (usec): min=96 , max=81543 , avg=11798.94, stdev=7735.60 > clat (usec): min=128 , max=140043 , avg=14835.85, stdev=11765.33 > clat (usec): min=109 , max=147207 , avg=11337.09, stdev=5990.35 > cpu : usr=15.93%, sys=60.37%, ctx=7764972, majf=0, minf=54 > cpu : usr=32.73%, sys=120.49%, ctx=7372945, majf=0, minf=1 > cpu : usr=18.84%, sys=58.18%, ctx=7775420, majf=0, minf=1 > cpu : usr=24.20%, sys=59.85%, ctx=8307886, majf=0, minf=0 > vdb: ios=8389107/8368136, merge=0/0, ticks=19457874/14616506, > in_queue=34206098, util=99.68% > 43: interrupt in total: 887320 > fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting > --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 > --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 > --filename=/dev/vdb --name=seq-read --stonewall --rw=read > --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall > --rw=randread --name=rnd-write --stonewall --rw=randwrite > > After: > ------------------------------------- > seq-read : io=0 B, bw=309503KB/s, iops=77375 , runt= 54207msec > seq-write : io=0 B, bw=448205KB/s, iops=112051 , runt= 37432msec > rand-read : io=0 B, bw=311254KB/s, iops=77813 , runt= 53902msec > rand-write: io=0 B, bw=377152KB/s, iops=94287 , runt= 44484msec > clat (usec): min=81 , max=90588 , avg=12946.06, stdev=9085.94 > clat (usec): min=57 , max=72264 , avg=8967.97, stdev=5951.04 > clat (usec): min=29 , max=101046 , avg=12889.95, stdev=9067.91 > clat (usec): min=52 , max=106152 , avg=10660.56, stdev=4778.19 > cpu : usr=15.05%, sys=57.92%, ctx=7710941, majf=0, minf=54 > cpu : usr=26.78%, sys=101.40%, ctx=7387891, majf=0, minf=2 > cpu : usr=19.03%, sys=58.17%, ctx=7681976, majf=0, minf=8 > cpu : usr=24.65%, sys=58.34%, ctx=8442632, majf=0, minf=4 > vdb: ios=8389086/8361888, merge=0/0, ticks=17243780/12742010, > in_queue=30078377, util=99.59% > 43: interrupt in total: 1259639 > fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting > --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 > --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 > --filename=/dev/vdb --name=seq-read --stonewall --rw=read > --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall > --rw=randread --name=rnd-write --stonewall --rw=randwrite > >> drivers/block/virtio_blk.c | 19 +++++++++++-------- >> 1 file changed, 11 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c >> index 53b81d5..0bdde8f 100644 >> --- a/drivers/block/virtio_blk.c >> +++ b/drivers/block/virtio_blk.c >> @@ -274,15 +274,18 @@ static void virtblk_done(struct virtqueue *vq) >> unsigned int len; >> >> spin_lock_irqsave(vblk->disk->queue->queue_lock, flags); >> - while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >> - if (vbr->bio) { >> - virtblk_bio_done(vbr); >> - bio_done = true; >> - } else { >> - virtblk_request_done(vbr); >> - req_done = true; >> + do { >> + virtqueue_disable_cb(vq); >> + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >> + if (vbr->bio) { >> + virtblk_bio_done(vbr); >> + bio_done = true; >> + } else { >> + virtblk_request_done(vbr); >> + req_done = true; >> + } >> } >> - } >> + } while (!virtqueue_enable_cb(vq)); >> /* In case queue is stopped waiting for more buffers. */ >> if (req_done) >> blk_start_queue(vblk->disk->queue); Fascinating. Please just confirm that VIRTIO_RING_F_EVENT_IDX is enabled? I forgot about the cool hack which MST put in to defer event updates using disable_cb/enable_cb. Applied! Rusty. ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-27 0:10 ` Rusty Russell @ 2012-09-27 6:48 ` Asias He 2012-09-28 6:08 ` Rusty Russell 2012-09-27 10:01 ` Paolo Bonzini ` (2 subsequent siblings) 3 siblings, 1 reply; 9+ messages in thread From: Asias He @ 2012-09-27 6:48 UTC (permalink / raw) To: Rusty Russell; +Cc: virtualization, kvm, Michael S. Tsirkin On 09/27/2012 08:10 AM, Rusty Russell wrote: > Asias He <asias@redhat.com> writes: > >> On 09/25/2012 10:36 AM, Asias He wrote: >>> This reduces unnecessary interrupts that host could send to guest while >>> guest is in the progress of irq handling. >>> >>> If one vcpu is handling the irq, while another interrupt comes, in >>> handle_edge_irq(), the guest will mask the interrupt via mask_msi_irq() >>> which is a very heavy operation that goes all the way down to host. >>> >>> Signed-off-by: Asias He <asias@redhat.com> >>> --- >> >> Here are some performance numbers on qemu: > > I assume this is with qemu using kvm, not qemu in soft emulation? :) Of course. > >> Before: >> ------------------------------------- >> seq-read : io=0 B, bw=269730KB/s, iops=67432 , runt= 62200msec >> seq-write : io=0 B, bw=339716KB/s, iops=84929 , runt= 49386msec >> rand-read : io=0 B, bw=270435KB/s, iops=67608 , runt= 62038msec >> rand-write: io=0 B, bw=354436KB/s, iops=88608 , runt= 47335msec >> clat (usec): min=101 , max=138052 , avg=14822.09, stdev=11771.01 >> clat (usec): min=96 , max=81543 , avg=11798.94, stdev=7735.60 >> clat (usec): min=128 , max=140043 , avg=14835.85, stdev=11765.33 >> clat (usec): min=109 , max=147207 , avg=11337.09, stdev=5990.35 >> cpu : usr=15.93%, sys=60.37%, ctx=7764972, majf=0, minf=54 >> cpu : usr=32.73%, sys=120.49%, ctx=7372945, majf=0, minf=1 >> cpu : usr=18.84%, sys=58.18%, ctx=7775420, majf=0, minf=1 >> cpu : usr=24.20%, sys=59.85%, ctx=8307886, majf=0, minf=0 >> vdb: ios=8389107/8368136, merge=0/0, ticks=19457874/14616506, >> in_queue=34206098, util=99.68% >> 43: interrupt in total: 887320 >> fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting >> --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 >> --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 >> --filename=/dev/vdb --name=seq-read --stonewall --rw=read >> --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall >> --rw=randread --name=rnd-write --stonewall --rw=randwrite >> >> After: >> ------------------------------------- >> seq-read : io=0 B, bw=309503KB/s, iops=77375 , runt= 54207msec >> seq-write : io=0 B, bw=448205KB/s, iops=112051 , runt= 37432msec >> rand-read : io=0 B, bw=311254KB/s, iops=77813 , runt= 53902msec >> rand-write: io=0 B, bw=377152KB/s, iops=94287 , runt= 44484msec >> clat (usec): min=81 , max=90588 , avg=12946.06, stdev=9085.94 >> clat (usec): min=57 , max=72264 , avg=8967.97, stdev=5951.04 >> clat (usec): min=29 , max=101046 , avg=12889.95, stdev=9067.91 >> clat (usec): min=52 , max=106152 , avg=10660.56, stdev=4778.19 >> cpu : usr=15.05%, sys=57.92%, ctx=7710941, majf=0, minf=54 >> cpu : usr=26.78%, sys=101.40%, ctx=7387891, majf=0, minf=2 >> cpu : usr=19.03%, sys=58.17%, ctx=7681976, majf=0, minf=8 >> cpu : usr=24.65%, sys=58.34%, ctx=8442632, majf=0, minf=4 >> vdb: ios=8389086/8361888, merge=0/0, ticks=17243780/12742010, >> in_queue=30078377, util=99.59% >> 43: interrupt in total: 1259639 >> fio --exec_prerun="echo 3 > /proc/sys/vm/drop_caches" --group_reporting >> --ioscheduler=noop --thread --bs=4k --size=512MB --direct=1 --numjobs=16 >> --ioengine=libaio --iodepth=64 --loops=3 --ramp_time=0 >> --filename=/dev/vdb --name=seq-read --stonewall --rw=read >> --name=seq-write --stonewall --rw=write --name=rnd-read --stonewall >> --rw=randread --name=rnd-write --stonewall --rw=randwrite >> >>> drivers/block/virtio_blk.c | 19 +++++++++++-------- >>> 1 file changed, 11 insertions(+), 8 deletions(-) >>> >>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c >>> index 53b81d5..0bdde8f 100644 >>> --- a/drivers/block/virtio_blk.c >>> +++ b/drivers/block/virtio_blk.c >>> @@ -274,15 +274,18 @@ static void virtblk_done(struct virtqueue *vq) >>> unsigned int len; >>> >>> spin_lock_irqsave(vblk->disk->queue->queue_lock, flags); >>> - while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >>> - if (vbr->bio) { >>> - virtblk_bio_done(vbr); >>> - bio_done = true; >>> - } else { >>> - virtblk_request_done(vbr); >>> - req_done = true; >>> + do { >>> + virtqueue_disable_cb(vq); >>> + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >>> + if (vbr->bio) { >>> + virtblk_bio_done(vbr); >>> + bio_done = true; >>> + } else { >>> + virtblk_request_done(vbr); >>> + req_done = true; >>> + } >>> } >>> - } >>> + } while (!virtqueue_enable_cb(vq)); >>> /* In case queue is stopped waiting for more buffers. */ >>> if (req_done) >>> blk_start_queue(vblk->disk->queue); > > Fascinating. Please just confirm that VIRTIO_RING_F_EVENT_IDX is > enabled? Sure. It is enabled ;-) > > I forgot about the cool hack which MST put in to defer event updates > using disable_cb/enable_cb. Hmm, are you talking about virtqueue_enable_cb_delayed()? > > Applied! > Rusty. > -- Asias ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-27 6:48 ` Asias He @ 2012-09-28 6:08 ` Rusty Russell 2012-09-28 7:03 ` Asias He 0 siblings, 1 reply; 9+ messages in thread From: Rusty Russell @ 2012-09-28 6:08 UTC (permalink / raw) To: Asias He; +Cc: virtualization, kvm, Michael S. Tsirkin Asias He <asias@redhat.com> writes: >> I forgot about the cool hack which MST put in to defer event updates >> using disable_cb/enable_cb. > > Hmm, are you talking about virtqueue_enable_cb_delayed()? Just the fact that virtqueue_disable_cb() prevents updates of used_index, and then we do the update in virtqueue_enable_cb(). Cheers, Rusty. ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-28 6:08 ` Rusty Russell @ 2012-09-28 7:03 ` Asias He 0 siblings, 0 replies; 9+ messages in thread From: Asias He @ 2012-09-28 7:03 UTC (permalink / raw) To: Rusty Russell; +Cc: virtualization, kvm, Michael S. Tsirkin On 09/28/2012 02:08 PM, Rusty Russell wrote: > Asias He <asias@redhat.com> writes: >>> I forgot about the cool hack which MST put in to defer event updates >>> using disable_cb/enable_cb. >> >> Hmm, are you talking about virtqueue_enable_cb_delayed()? > > Just the fact that virtqueue_disable_cb() prevents updates of > used_index, and then we do the update in virtqueue_enable_cb(). Okay. -- Asias ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-27 0:10 ` Rusty Russell 2012-09-27 6:48 ` Asias He @ 2012-09-27 10:01 ` Paolo Bonzini 2012-09-28 8:32 ` Michael S. Tsirkin [not found] ` <50642400.5030906@redhat.com> 3 siblings, 0 replies; 9+ messages in thread From: Paolo Bonzini @ 2012-09-27 10:01 UTC (permalink / raw) To: Rusty Russell; +Cc: Michael S. Tsirkin, kvm, virtualization Il 27/09/2012 02:10, Rusty Russell ha scritto: >>> >> + do { >>> >> + virtqueue_disable_cb(vq); >>> >> + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >>> >> + if (vbr->bio) { >>> >> + virtblk_bio_done(vbr); >>> >> + bio_done = true; >>> >> + } else { >>> >> + virtblk_request_done(vbr); >>> >> + req_done = true; >>> >> + } >>> >> } >>> >> - } >>> >> + } while (!virtqueue_enable_cb(vq)); >>> >> /* In case queue is stopped waiting for more buffers. */ >>> >> if (req_done) >>> >> blk_start_queue(vblk->disk->queue); > Fascinating. Please just confirm that VIRTIO_RING_F_EVENT_IDX is > enabled? Yeah, it's a nice and cheap trick. Stefan, I see that you had this in virtio-scsi since even before I picked it up. Do you remember how you came up with it? Paolo ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() 2012-09-27 0:10 ` Rusty Russell 2012-09-27 6:48 ` Asias He 2012-09-27 10:01 ` Paolo Bonzini @ 2012-09-28 8:32 ` Michael S. Tsirkin [not found] ` <50642400.5030906@redhat.com> 3 siblings, 0 replies; 9+ messages in thread From: Michael S. Tsirkin @ 2012-09-28 8:32 UTC (permalink / raw) To: Rusty Russell; +Cc: kvm, virtualization On Thu, Sep 27, 2012 at 09:40:03AM +0930, Rusty Russell wrote: > I forgot about the cool hack which MST put in to defer event updates > using disable_cb/enable_cb. I considered sticking some invalid value in event index on disable but in my testing it did not seem to give any gain, and knowing actual index of the other side is better for debugging. -- MST ^ permalink raw reply [flat|nested] 9+ messages in thread
[parent not found: <50642400.5030906@redhat.com>]
* Re: [PATCH] virtio-blk: Disable callback in virtblk_done() [not found] ` <50642400.5030906@redhat.com> @ 2012-10-02 14:42 ` Stefan Hajnoczi 0 siblings, 0 replies; 9+ messages in thread From: Stefan Hajnoczi @ 2012-10-02 14:42 UTC (permalink / raw) To: Paolo Bonzini; +Cc: Michael S. Tsirkin, kvm, virtualization On Thu, Sep 27, 2012 at 12:01 PM, Paolo Bonzini <pbonzini@redhat.com> wrote: > Il 27/09/2012 02:10, Rusty Russell ha scritto: >>>> >> + do { >>>> >> + virtqueue_disable_cb(vq); >>>> >> + while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { >>>> >> + if (vbr->bio) { >>>> >> + virtblk_bio_done(vbr); >>>> >> + bio_done = true; >>>> >> + } else { >>>> >> + virtblk_request_done(vbr); >>>> >> + req_done = true; >>>> >> + } >>>> >> } >>>> >> - } >>>> >> + } while (!virtqueue_enable_cb(vq)); >>>> >> /* In case queue is stopped waiting for more buffers. */ >>>> >> if (req_done) >>>> >> blk_start_queue(vblk->disk->queue); >> Fascinating. Please just confirm that VIRTIO_RING_F_EVENT_IDX is >> enabled? > > Yeah, it's a nice and cheap trick. Stefan, I see that you had this in > virtio-scsi since even before I picked it up. Do you remember how you > came up with it? I've played with disable_cb/enable_cb previously in virtio-blk and virtio-scsi when aliguori had suggested reducing notifies. I definitely didn't invent it :). Stefan ^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2012-10-02 14:42 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
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2012-09-25 2:36 [PATCH] virtio-blk: Disable callback in virtblk_done() Asias He
2012-09-25 14:08 ` Asias He
2012-09-27 0:10 ` Rusty Russell
2012-09-27 6:48 ` Asias He
2012-09-28 6:08 ` Rusty Russell
2012-09-28 7:03 ` Asias He
2012-09-27 10:01 ` Paolo Bonzini
2012-09-28 8:32 ` Michael S. Tsirkin
[not found] ` <50642400.5030906@redhat.com>
2012-10-02 14:42 ` Stefan Hajnoczi
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