search for: vhost_vq_avail_empti

On Mon, Jan 09, 2017 at 10:59:16AM +0800, Jason Wang wrote: > > > On 2017?01?07? 03:55, Michael S. Tsirkin wrote: > > On Fri, Jan 06, 2017 at 10:13:15AM +0800, Jason Wang wrote: > > > This patch tries to do several tweaks on vhost_vq_avail_empty() for a > > > better performance: > > > > > > - check cached avail index first which could avoid

On Mon, Jan 09, 2017 at 10:59:16AM +0800, Jason Wang wrote: > > > On 2017?01?07? 03:55, Michael S. Tsirkin wrote: > > On Fri, Jan 06, 2017 at 10:13:15AM +0800, Jason Wang wrote: > > > This patch tries to do several tweaks on vhost_vq_avail_empty() for a > > > better performance: > > > > > > - check cached avail index first which could avoid

On Fri, Jan 06, 2017 at 10:13:15AM +0800, Jason Wang wrote: > This patch tries to do several tweaks on vhost_vq_avail_empty() for a > better performance: > > - check cached avail index first which could avoid userspace memory access. > - using unlikely() for the failure of userspace access > - check vq->last_avail_idx instead of cached avail index as the last > step.

On Fri, Jan 06, 2017 at 10:13:15AM +0800, Jason Wang wrote: > This patch tries to do several tweaks on vhost_vq_avail_empty() for a > better performance: > > - check cached avail index first which could avoid userspace memory access. > - using unlikely() for the failure of userspace access > - check vq->last_avail_idx instead of cached avail index as the last > step.

On 2018/07/24 2:31, Tonghao Zhang wrote: > On Mon, Jul 23, 2018 at 10:20 PM Toshiaki Makita > <toshiaki.makita1 at gmail.com> wrote: >> >> On 18/07/23 (?) 21:43, Tonghao Zhang wrote: >>> On Mon, Jul 23, 2018 at 5:58 PM Toshiaki Makita >>> <makita.toshiaki at lab.ntt.co.jp> wrote: >>>> >>>> On 2018/07/22 3:04, xiangxia.m.yue at

On 2018/07/24 2:31, Tonghao Zhang wrote: > On Mon, Jul 23, 2018 at 10:20 PM Toshiaki Makita > <toshiaki.makita1 at gmail.com> wrote: >> >> On 18/07/23 (?) 21:43, Tonghao Zhang wrote: >>> On Mon, Jul 23, 2018 at 5:58 PM Toshiaki Makita >>> <makita.toshiaki at lab.ntt.co.jp> wrote: >>>> >>>> On 2018/07/22 3:04, xiangxia.m.yue at

On 2018/07/22 3:04, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com> > --- ... >

On 2018/07/22 3:04, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com> > --- ... >

We check tx avail through vhost_enable_notify() in the past which is wrong since it only checks whether or not guest has filled more available buffer since last avail idx synchronization which was just done by vhost_vq_avail_empty() before. What we really want is checking pending buffers in the avail ring. Fix this by calling vhost_vq_avail_empty() instead. This issue could be noticed by doing

We check tx avail through vhost_enable_notify() in the past which is wrong since it only checks whether or not guest has filled more available buffer since last avail idx synchronization which was just done by vhost_vq_avail_empty() before. What we really want is checking pending buffers in the avail ring. Fix this by calling vhost_vq_avail_empty() instead. This issue could be noticed by doing

Under heavy load vhost tx busypoll tend not to suppress vq kicks, which causes poor guest tx performance. The detailed scenario is described in commitlog of patch 2. Rx seems not to have that serious problem, but for consistency I made a similar change on rx to avoid rx wakeups (patch 3). Additionary patch 4 is to avoid rx kicks under heavy load during busypoll. Tx performance is greatly improved

On 2018?08?01? 11:00, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > In the handle_tx, the busypoll will vhost_net_disable/enable_vq > because we

On 2018?08?01? 11:00, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > In the handle_tx, the busypoll will vhost_net_disable/enable_vq > because we

From: Tonghao Zhang <xiangxia.m.yue at gmail.com> Factor out generic busy polling logic and will be used for in tx path in the next patch. And with the patch, qemu can set differently the busyloop_timeout for rx queue. Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com> --- drivers/vhost/net.c | 114 ++++++++++++++++++++++++++++++++++------------------ 1 file changed, 74

On 2017?01?10? 07:10, Michael S. Tsirkin wrote: > On Mon, Jan 09, 2017 at 10:59:16AM +0800, Jason Wang wrote: >> >> On 2017?01?07? 03:55, Michael S. Tsirkin wrote: >>> On Fri, Jan 06, 2017 at 10:13:15AM +0800, Jason Wang wrote: >>>> This patch tries to do several tweaks on vhost_vq_avail_empty() for a >>>> better performance: >>>>

On 2018?07?02? 20:57, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > Signed-off-by: Tonghao Zhang <zhangtonghao at didichuxing.com> > --- >

On 2018?07?02? 20:57, xiangxia.m.yue at gmail.com wrote: > From: Tonghao Zhang <xiangxia.m.yue at gmail.com> > > Factor out generic busy polling logic and will be > used for in tx path in the next patch. And with the patch, > qemu can set differently the busyloop_timeout for rx queue. > > Signed-off-by: Tonghao Zhang <zhangtonghao at didichuxing.com> > --- >

Under heavy load vhost busypoll may run without suppressing notification. For example tx zerocopy callback can push tx work while handle_tx() is running, then busyloop exits due to vhost_has_work() condition and enables notification but immediately reenters handle_tx() because the pushed work was tx. In this case handle_tx() tries to disable notification again, but when using event_idx it by

Under heavy load vhost busypoll may run without suppressing notification. For example tx zerocopy callback can push tx work while handle_tx() is running, then busyloop exits due to vhost_has_work() condition and enables notification but immediately reenters handle_tx() because the pushed work was tx. In this case handle_tx() tries to disable notification again, but when using event_idx it by

Hi Jason, On 2018/06/29 18:30, Jason Wang wrote: > On 2018?06?29? 16:09, Toshiaki Makita wrote: ... >> To fix this, poll the work instead of enabling notification when >> busypoll is interrupted by something. IMHO signal_pending() and >> vhost_has_work() are kind of interruptions rather than signals to >> completely cancel the busypoll, so let's run busypoll after