similar to: [PATCH net-next v2 0/5] virtio-net tx napi

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

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v2 -> v3: - convert __netif_tx_trylock to __netif_tx_lock on tx napi poll ensure that the handler always cleans, to avoid deadlock - unconditionally clean in start_xmit avoid adding an unnecessary "if (use_napi)" branch - remove

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v2 -> v3: - convert __netif_tx_trylock to __netif_tx_lock on tx napi poll ensure that the handler always cleans, to avoid deadlock - unconditionally clean in start_xmit avoid adding an unnecessary "if (use_napi)" branch - remove

From: Willem de Bruijn <willemb at google.com> As of tx napi, device down (`ip link set dev $dev down`) hangs unless tx napi is enabled. Else napi_enable is not called, so napi_disable will spin on test_and_set_bit NAPI_STATE_SCHED. Only call napi_disable if tx napi is enabled. Fixes: 5a719c2552ca ("virtio-net: transmit napi") Reported-by: Jason Wang <jasowang at

From: Willem de Bruijn <willemb at google.com> As of tx napi, device down (`ip link set dev $dev down`) hangs unless tx napi is enabled. Else napi_enable is not called, so napi_disable will spin on test_and_set_bit NAPI_STATE_SCHED. Only call napi_disable if tx napi is enabled. Fixes: 5a719c2552ca ("virtio-net: transmit napi") Reported-by: Jason Wang <jasowang at

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 2018/12/26 ??11:22, Michael S. Tsirkin wrote: > On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote: >> On 2018/12/6 ??6:54, Michael S. Tsirkin wrote: >>> When use_napi is set, let's enable BQLs. Note: some of the issues are >>> similar to wifi. It's worth considering whether something similar to >>> commit 36148c2bbfbe ("mac80211:

On 2018/12/26 ??11:22, Michael S. Tsirkin wrote: > On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote: >> On 2018/12/6 ??6:54, Michael S. Tsirkin wrote: >>> When use_napi is set, let's enable BQLs. Note: some of the issues are >>> similar to wifi. It's worth considering whether something similar to >>> commit 36148c2bbfbe ("mac80211:

From: Willem de Bruijn <willemb at google.com> Amortize the cost of virtual interrupts by doing both rx and tx work on reception of a receive interrupt if tx napi is enabled. With VIRTIO_F_EVENT_IDX, this suppresses most explicit tx completion interrupts for bidirectional workloads. Signed-off-by: Willem de Bruijn <willemb at google.com> --- drivers/net/virtio_net.c | 22

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 2018/12/6 ??6:54, Michael S. Tsirkin wrote: > When use_napi is set, let's enable BQLs. Note: some of the issues are > similar to wifi. It's worth considering whether something similar to > commit 36148c2bbfbe ("mac80211: Adjust TSQ pacing shift") might be > benefitial. I've played a similar patch several days before. The tricky part is the mode switching

On 2018/12/6 ??6:54, Michael S. Tsirkin wrote: > When use_napi is set, let's enable BQLs. Note: some of the issues are > similar to wifi. It's worth considering whether something similar to > commit 36148c2bbfbe ("mac80211: Adjust TSQ pacing shift") might be > benefitial. I've played a similar patch several days before. The tricky part is the mode switching

Now that we have brought the virtio overhead way down with a fast packed ring implementation, we seem to be actually observing TCP drops indicative of bufferbloat. So let's try to enable TSQ. Note: it isn't clear that the default pacing is great for the virt usecase. It's worth trying to play with sk_pacing_shift_update to see what happens. For this reason, and for a more important

On Mon, Apr 24, 2017 at 12:40 PM, Michael S. Tsirkin <mst at redhat.com> wrote: > On Fri, Apr 21, 2017 at 10:50:12AM -0400, Willem de Bruijn wrote: >> >>> Maybe I was wrong, but according to Michael's comment it looks like he >> >>> want >> >>> check affinity_hint_set just for speculative tx polling on rx napi >> >>> instead

On Mon, Apr 24, 2017 at 12:40 PM, Michael S. Tsirkin <mst at redhat.com> wrote: > On Fri, Apr 21, 2017 at 10:50:12AM -0400, Willem de Bruijn wrote: >> >>> Maybe I was wrong, but according to Michael's comment it looks like he >> >>> want >> >>> check affinity_hint_set just for speculative tx polling on rx napi >> >>> instead

On 2018/12/26 ??11:19, Michael S. Tsirkin wrote: > On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote: >> On 2018/12/6 ??6:54, Michael S. Tsirkin wrote: >>> When use_napi is set, let's enable BQLs. Note: some of the issues are >>> similar to wifi. It's worth considering whether something similar to >>> commit 36148c2bbfbe ("mac80211:

On 2018/12/26 ??11:19, Michael S. Tsirkin wrote: > On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote: >> On 2018/12/6 ??6:54, Michael S. Tsirkin wrote: >>> When use_napi is set, let's enable BQLs. Note: some of the issues are >>> similar to wifi. It's worth considering whether something similar to >>> commit 36148c2bbfbe ("mac80211:

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> ---