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authorWillem de Bruijn <willemb@google.com>2019-06-13 12:24:57 -0400
committerDavid S. Miller <davem@davemloft.net>2019-06-14 19:34:27 -0700
commit31c03aef9bc22a64a8324d650ca4198819ef3a33 (patch)
treef899165551f74efdad63d2542c0e21ecb22dfbb9 /drivers/net/virtio_net.c
parent87f373921c4ed770abdb3cdafd796ef7f7b86620 (diff)
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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 <willemb@google.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/virtio_net.c')
-rw-r--r--drivers/net/virtio_net.c2
1 files changed, 1 insertions, 1 deletions
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);