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...I noticed this in the past too. > >> Though this is not limited to napi-tx, it is more >> pronounced in that mode than without napi. >> >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: >> >> upstream: >> >> 1,1,1: 28985 Mbps, 278 Gcyc >> 1,0,2: 30067 Mbps, 402 Gcyc >> >> napi tx: >> >> 1,1,1: 34492 Mbps, 269 Gcyc >> 1,0,2: 36527 Mbps, 537 Gcyc (!) >> 1,0,1: 36269 Mbps, 394 Gcyc >> 1,0,0: 34674 Mbps, 402 Gcyc >> >> This is a particularly strong example. It is also repres...

...I noticed this in the past too. > >> Though this is not limited to napi-tx, it is more >> pronounced in that mode than without napi. >> >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: >> >> upstream: >> >> 1,1,1: 28985 Mbps, 278 Gcyc >> 1,0,2: 30067 Mbps, 402 Gcyc >> >> napi tx: >> >> 1,1,1: 34492 Mbps, 269 Gcyc >> 1,0,2: 36527 Mbps, 537 Gcyc (!) >> 1,0,1: 36269 Mbps, 394 Gcyc >> 1,0,0: 34674 Mbps, 402 Gcyc >> >> This is a particularly strong example. It is also repres...

...affinity. The cycle cost is significant without affinity regardless of whether the optimization is used. Though this is not limited to napi-tx, it is more pronounced in that mode than without napi. 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: upstream: 1,1,1: 28985 Mbps, 278 Gcyc 1,0,2: 30067 Mbps, 402 Gcyc napi tx: 1,1,1: 34492 Mbps, 269 Gcyc 1,0,2: 36527 Mbps, 537 Gcyc (!) 1,0,1: 36269 Mbps, 394 Gcyc 1,0,0: 34674 Mbps, 402 Gcyc This is a particularly strong example. It is also representative of most RR tests. It is less pronounced in other streaming tests. 10x TCP_RR,...

...affinity. The cycle cost is significant without affinity regardless of whether the optimization is used. Though this is not limited to napi-tx, it is more pronounced in that mode than without napi. 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: upstream: 1,1,1: 28985 Mbps, 278 Gcyc 1,0,2: 30067 Mbps, 402 Gcyc napi tx: 1,1,1: 34492 Mbps, 269 Gcyc 1,0,2: 36527 Mbps, 537 Gcyc (!) 1,0,1: 36269 Mbps, 394 Gcyc 1,0,0: 34674 Mbps, 402 Gcyc This is a particularly strong example. It is also representative of most RR tests. It is less pronounced in other streaming tests. 10x TCP_RR,...

...ot limited to napi-tx, it is more >> >> pronounced in that mode than without napi. >> >> >> >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: >> >> >> >> upstream: >> >> >> >> 1,1,1: 28985 Mbps, 278 Gcyc >> >> 1,0,2: 30067 Mbps, 402 Gcyc >> >> >> >> napi tx: >> >> >> >> 1,1,1: 34492 Mbps, 269 Gcyc >> >> 1,0,2: 36527 Mbps, 537 Gcyc (!) >> >> 1,0,1: 36269 Mbps, 394 Gcyc >> >> 1,0,0: 34674 Mbps, 402 Gcyc &g...

...ot limited to napi-tx, it is more >> >> pronounced in that mode than without napi. >> >> >> >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: >> >> >> >> upstream: >> >> >> >> 1,1,1: 28985 Mbps, 278 Gcyc >> >> 1,0,2: 30067 Mbps, 402 Gcyc >> >> >> >> napi tx: >> >> >> >> 1,1,1: 34492 Mbps, 269 Gcyc >> >> 1,0,2: 36527 Mbps, 537 Gcyc (!) >> >> 1,0,1: 36269 Mbps, 394 Gcyc >> >> 1,0,0: 34674 Mbps, 402 Gcyc &g...

...the > optimization is used. Yes, I noticed this in the past too. > Though this is not limited to napi-tx, it is more > pronounced in that mode than without napi. > > 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: > > upstream: > > 1,1,1: 28985 Mbps, 278 Gcyc > 1,0,2: 30067 Mbps, 402 Gcyc > > napi tx: > > 1,1,1: 34492 Mbps, 269 Gcyc > 1,0,2: 36527 Mbps, 537 Gcyc (!) > 1,0,1: 36269 Mbps, 394 Gcyc > 1,0,0: 34674 Mbps, 402 Gcyc > > This is a particularly strong example. It is also representative > of most RR tests. It is le...

...t; >> Though this is not limited to napi-tx, it is more > >> pronounced in that mode than without napi. > >> > >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: > >> > >> upstream: > >> > >> 1,1,1: 28985 Mbps, 278 Gcyc > >> 1,0,2: 30067 Mbps, 402 Gcyc > >> > >> napi tx: > >> > >> 1,1,1: 34492 Mbps, 269 Gcyc > >> 1,0,2: 36527 Mbps, 537 Gcyc (!) > >> 1,0,1: 36269 Mbps, 394 Gcyc > >> 1,0,0: 34674 Mbps, 402 Gcyc > >> > >> This i...

...gt; >> >> pronounced in that mode than without napi. > >> >> > >> >> 1x TCP_RR for affinity configuration {process, rx_irq, tx_irq}: > >> >> > >> >> upstream: > >> >> > >> >> 1,1,1: 28985 Mbps, 278 Gcyc > >> >> 1,0,2: 30067 Mbps, 402 Gcyc > >> >> > >> >> napi tx: > >> >> > >> >> 1,1,1: 34492 Mbps, 269 Gcyc > >> >> 1,0,2: 36527 Mbps, 537 Gcyc (!) > >> >> 1,0,1: 36269 Mbps, 394 Gcyc > >>...

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