similar to: [PATCH RFC v2 1/3] virtio_net: enable tx interrupt

On newer hosts that support delayed tx interrupts, we probably don't have much to gain from orphaning packets early. Based on patch by Jason Wang. Note: this will likely degrade performance for hosts without event idx support. Various fallback options are available, including orphaning conditionally. Testing TBD. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> ---

On newer hosts that support delayed tx interrupts, we probably don't have much to gain from orphaning packets early. Based on patch by Jason Wang. Note: this will likely degrade performance for hosts without event idx support. Various fallback options are available, including orphaning conditionally. Testing TBD. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> ---

Orphan skb in ndo_start_xmit() breaks socket accounting and packet queuing. This in fact breaks lots of things such as pktgen and several TCP optimizations. And also make BQL can't be implemented for virtio-net. This patch tries to solve this issue by enabling tx interrupt. To avoid introducing extra spinlocks, a tx napi was scheduled to free those packets. More tx interrupt mitigation

Orphan skb in ndo_start_xmit() breaks socket accounting and packet queuing. This in fact breaks lots of things such as pktgen and several TCP optimizations. And also make BQL can't be implemented for virtio-net. This patch tries to solve this issue by enabling tx interrupt. To avoid introducing extra spinlocks, a tx napi was scheduled to free those packets. More tx interrupt mitigation

Improve tx batching using byte queue limits. Should be especially effective for MQ. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index a9bf178..8dea411 100644 --- a/drivers/net/virtio_net.c +++

Improve tx batching using byte queue limits. Should be especially effective for MQ. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index a9bf178..8dea411 100644 --- a/drivers/net/virtio_net.c +++

On Mon, Dec 01, 2014 at 06:17:04PM +0800, Jason Wang wrote: > On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Note: this might degrade performance for > hosts without event idx support. > Should be addressed by the next patch. > > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc:

On Mon, Dec 01, 2014 at 06:17:04PM +0800, Jason Wang wrote: > On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Note: this might degrade performance for > hosts without event idx support. > Should be addressed by the next patch. > > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc:

We free transmitted packets in ndo_start_xmit() in the past to get better performance in the past. One side effect is that skb_orphan() needs to be called in ndo_start_xmit() which makes sk_wmem_alloc not accurate in fact. For TCP protocol, this means several optimization could not work well such as TCP small queue and auto corking. This can lead extra low throughput of small packets stream.

We free transmitted packets in ndo_start_xmit() in the past to get better performance in the past. One side effect is that skb_orphan() needs to be called in ndo_start_xmit() which makes sk_wmem_alloc not accurate in fact. For TCP protocol, this means several optimization could not work well such as TCP small queue and auto corking. This can lead extra low throughput of small packets stream.

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

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

From: Willem de Bruijn <willemb at google.com> Convert virtio-net to a standard napi tx completion path. This enables better TCP pacing using TCP small queues and increases single stream throughput. The virtio-net driver currently cleans tx descriptors on transmission of new packets in ndo_start_xmit. Latency depends on new traffic, so is unbounded. To avoid deadlock when a socket reaches

On Wed, Oct 15, 2014 at 03:25:29PM +0800, Jason Wang wrote: > Orphan skb in ndo_start_xmit() breaks socket accounting and packet > queuing. This in fact breaks lots of things such as pktgen and several > TCP optimizations. And also make BQL can't be implemented for > virtio-net. > > This patch tries to solve this issue by enabling tx interrupt. To > avoid introducing

On 10/15/2014 05:53 AM, Michael S. Tsirkin wrote: > On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Based on patch by Jason Wang. > > Note: this will likely degrade performance for hosts without event idx > support. Various fallback options are available, including > orphaning

On 2014/12/1 18:17, Jason Wang wrote: > On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Note: this might degrade performance for > hosts without event idx support. > Should be addressed by the next patch. > > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc: Michael S. Tsirkin

On 2014/12/1 18:17, Jason Wang wrote: > On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Note: this might degrade performance for > hosts without event idx support. > Should be addressed by the next patch. > > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc: Michael S. Tsirkin

On Sat, Oct 11, 2014 at 03:16:46PM +0800, Jason Wang wrote: > We free transmitted packets in ndo_start_xmit() in the past to get better > performance in the past. One side effect is that skb_orphan() needs to be > called in ndo_start_xmit() which makes sk_wmem_alloc not accurate in > fact. For TCP protocol, this means several optimization could not work well > such as TCP small

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Based on previous patchsets by Jason Wang: [RFC V7 PATCH 0/7] enable tx interrupts for virtio-net http://lkml.iu.edu/hypermail/linux/kernel/1505.3/00245.html Changes: RFC -> v1: - dropped vhost interrupt moderation patch: not needed and likely expensive at light

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Based on previous patchsets by Jason Wang: [RFC V7 PATCH 0/7] enable tx interrupts for virtio-net http://lkml.iu.edu/hypermail/linux/kernel/1505.3/00245.html Changes: RFC -> v1: - dropped vhost interrupt moderation patch: not needed and likely expensive at light