From: Willem de Bruijn Date: Thu, 13 Jun 2019 16:24:57 +0000 (-0400) Subject: virtio_net: enable napi_tx by default X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=31c03aef9bc22a64a8324d650ca4198819ef3a33;p=openwrt%2Fstaging%2Fblogic.git virtio_net: enable napi_tx by default NAPI tx mode improves TCP behavior by enabling TCP small queues (TSQ). TSQ reduces queuing ("bufferbloat") and burstiness. Previous measurements have shown significant improvement for TCP_STREAM style workloads. Such as those in commit 86a5df1495cc ("Merge branch 'virtio-net-tx-napi'"). There has been uncertainty about smaller possible regressions in latency due to increased reliance on tx interrupts. The above results did not show that, nor did I observe this when rerunning TCP_RR on Linux 5.1 this week on a pair of guests in the same rack. This may be subject to other settings, notably interrupt coalescing. In the unlikely case of regression, we have landed a credible runtime solution. Ethtool can configure it with -C tx-frames [0|1] as of commit 0c465be183c7 ("virtio_net: ethtool tx napi configuration"). NAPI tx mode has been the default in Google Container-Optimized OS (COS) for over half a year, as of release M70 in October 2018, without any negative reports. Link: https://marc.info/?l=linux-netdev&m=149305618416472 Link: https://lwn.net/Articles/507065/ Signed-off-by: Willem de Bruijn Acked-by: Michael S. Tsirkin Acked-by: Jason Wang Signed-off-by: David S. Miller --- diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 0d4115c9e20b..4f3de0ac8b0b 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -26,7 +26,7 @@ static int napi_weight = NAPI_POLL_WEIGHT; module_param(napi_weight, int, 0444); -static bool csum = true, gso = true, napi_tx; +static bool csum = true, gso = true, napi_tx = true; module_param(csum, bool, 0444); module_param(gso, bool, 0444); module_param(napi_tx, bool, 0644);