similar to: [PATCH 1/2] virtio: support unlocked queue poll

This adds a way to check ring empty state after enable_cb outside any locks. Will be used by virtio_net. Note: there's room for more optimization: caller is likely to have a memory barrier already, which means we might be able to get rid of a barrier here. Deferring this optimization until we do some benchmarking. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> ---

This adds a way to check ring empty state after enable_cb outside any locks. Will be used by virtio_net. Note: there's room for more optimization: caller is likely to have a memory barrier already, which means we might be able to get rid of a barrier here. Deferring this optimization until we do some benchmarking. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> ---

On 10/15/2014 05:28 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:26PM +0800, Jason Wang wrote: >> This patch introduces virtio_enable_cb_avail() to publish avail idx >> and used event. This could be used by batched buffer submitting to >> reduce the number of tx interrupts. >> >> Cc: Rusty Russell <rusty at rustcorp.com.au> >> Cc:

On 10/15/2014 05:28 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:26PM +0800, Jason Wang wrote: >> This patch introduces virtio_enable_cb_avail() to publish avail idx >> and used event. This could be used by batched buffer submitting to >> reduce the number of tx interrupts. >> >> Cc: Rusty Russell <rusty at rustcorp.com.au> >> Cc:

This patch introduces virtio_enable_cb_avail() to publish avail idx and used event. This could be used by batched buffer submitting to reduce the number of tx interrupts. Cc: Rusty Russell <rusty at rustcorp.com.au> Cc: Michael S. Tsirkin <mst at redhat.com> Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/virtio/virtio_ring.c | 22 ++++++++++++++++++++--

This patch introduces virtio_enable_cb_avail() to publish avail idx and used event. This could be used by batched buffer submitting to reduce the number of tx interrupts. Cc: Rusty Russell <rusty at rustcorp.com.au> Cc: Michael S. Tsirkin <mst at redhat.com> Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/virtio/virtio_ring.c | 22 ++++++++++++++++++++--

On 10/15/2014 06:41 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 06:19:15PM +0800, Jason Wang wrote: >> On 10/15/2014 05:28 PM, Michael S. Tsirkin wrote: >>> On Wed, Oct 15, 2014 at 03:25:26PM +0800, Jason Wang wrote: >>>> This patch introduces virtio_enable_cb_avail() to publish avail idx >>>> and used event. This could be used by batched

On 10/15/2014 06:41 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 06:19:15PM +0800, Jason Wang wrote: >> On 10/15/2014 05:28 PM, Michael S. Tsirkin wrote: >>> On Wed, Oct 15, 2014 at 03:25:26PM +0800, Jason Wang wrote: >>>> This patch introduces virtio_enable_cb_avail() to publish avail idx >>>> and used event. This could be used by batched

On Fri, 2013-07-12 at 23:13 +0200, Wolfram Gloger wrote: > Hi, > > Today I merged M. Tsirkin's patch v2 "virtio_net: fix race in RX VQ > processing": > > http://lkml.indiana.edu/hypermail/linux/kernel/1307.1/00503.html > > into 3.2.48 and lightly tested the result (vhost-net, virtio-disk > and 9pfs using virtio). This sounds like it could be suitable

On Fri, 2013-07-12 at 23:13 +0200, Wolfram Gloger wrote: > Hi, > > Today I merged M. Tsirkin's patch v2 "virtio_net: fix race in RX VQ > processing": > > http://lkml.indiana.edu/hypermail/linux/kernel/1307.1/00503.html > > into 3.2.48 and lightly tested the result (vhost-net, virtio-disk > and 9pfs using virtio). This sounds like it could be suitable

virtio net called virtqueue_enable_cq on RX path after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE. Jason Wang reports that he can trigger

Below should be useful for some experiments Jason is doing. I thought I'd send it out for early review/feedback. event idx feature allows us to defer interrupts until a specific # of descriptors were used. Sometimes it might be useful to get an interrupt after a specific descriptor, regardless. This adds a descriptor flag for this, and an API to create an urgent output descriptor. This is

virtio net called virtqueue_enable_cq on RX path after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE. Jason Wang reports that he can trigger

Below should be useful for some experiments Jason is doing. I thought I'd send it out for early review/feedback. event idx feature allows us to defer interrupts until a specific # of descriptors were used. Sometimes it might be useful to get an interrupt after a specific descriptor, regardless. This adds a descriptor flag for this, and an API to create an urgent output descriptor. This is

On 10/15/2014 05:34 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:25PM +0800, Jason Wang wrote: >> This patch checks the new event idx to make sure used event idx never >> goes back. This is used to synchronize the calls between >> virtqueue_enable_cb_delayed() and virtqueue_enable_cb(). >> >> Cc: Rusty Russell <rusty at rustcorp.com.au>

On 10/15/2014 05:34 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:25PM +0800, Jason Wang wrote: >> This patch checks the new event idx to make sure used event idx never >> goes back. This is used to synchronize the calls between >> virtqueue_enable_cb_delayed() and virtqueue_enable_cb(). >> >> Cc: Rusty Russell <rusty at rustcorp.com.au>

On Sat, Oct 11, 2014 at 03:16:44PM +0800, Jason Wang wrote: > Below should be useful for some experiments Jason is doing. > I thought I'd send it out for early review/feedback. > > event idx feature allows us to defer interrupts until > a specific # of descriptors were used. > Sometimes it might be useful to get an interrupt after > a specific descriptor, regardless. >

On 10/15/2014 06:32 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 06:13:19PM +0800, Jason Wang wrote: >> On 10/15/2014 05:34 PM, Michael S. Tsirkin wrote: >>> On Wed, Oct 15, 2014 at 03:25:25PM +0800, Jason Wang wrote: >>>> This patch checks the new event idx to make sure used event idx never >>>> goes back. This is used to synchronize the calls

On 10/15/2014 06:32 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 06:13:19PM +0800, Jason Wang wrote: >> On 10/15/2014 05:34 PM, Michael S. Tsirkin wrote: >>> On Wed, Oct 15, 2014 at 03:25:25PM +0800, Jason Wang wrote: >>>> This patch checks the new event idx to make sure used event idx never >>>> goes back. This is used to synchronize the calls

According to David, proper accounting and queueing (at all levels, not just TCP sockets) is more important than trying to skim a bunch of cycles by avoiding TX interrupts. Having an event to free the SKB is absolutely essential for the stack to operate correctly. This series tries to enable tx interrupt for virtio-net. The idea is simple: enable tx interrupt and schedule a tx napi to free old