From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jason Wang <jasowang@redhat.com>
Cc: David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>,
Yuchung Cheng <ycheng@google.com>,
Neal Cardwell <ncardwell@google.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v2 net-next] pkt_sched: fq: Fair Queue packet scheduler
Date: Tue, 03 Sep 2013 22:59:36 -0700 [thread overview]
Message-ID: <1378274376.7360.82.camel@edumazet-glaptop> (raw)
In-Reply-To: <5226C4A0.6040709@redhat.com>
On Wed, 2013-09-04 at 13:26 +0800, Jason Wang wrote:
> I see both degradation and jitter when using fq with virtio-net. Guest
> to guest performance drops from 8Gb/s to 3Gb/s-7Gb/s. Guest to local
> host drops from 8Gb/s to 4Gb/s-6Gb/s. Guest to external host with ixgbe
> drops from 9Gb/s to 7Gb/s
>
> I didn't meet the issue when using sfq or disabling pacing.
>
> So it looks like it was caused by the inaccuracy and jitter of the
> pacing estimation in a virt guest?
Well, using virtio-net means you use FQ without pacing.
Make sure you do not have reorders because of a bug in queue selection.
TCP stack has the ooo_okay thing, I do not think a VM can get it.
nstat >/dev/null ; <your test> ; nstat
And tcpdump would certainly help ;)
next prev parent reply other threads:[~2013-09-04 5:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-29 22:49 [PATCH v2 net-next] pkt_sched: fq: Fair Queue packet scheduler Eric Dumazet
2013-08-30 1:47 ` David Miller
2013-08-30 2:30 ` [PATCH iproute2] " Eric Dumazet
2013-09-03 15:49 ` Stephen Hemminger
2013-09-04 5:26 ` [PATCH v2 net-next] " Jason Wang
2013-09-04 5:59 ` Eric Dumazet [this message]
2013-09-04 6:30 ` Jason Wang
2013-09-04 10:30 ` Eric Dumazet
2013-09-04 11:27 ` Eric Dumazet
2013-09-04 11:59 ` Daniel Borkmann
2013-09-05 3:39 ` Jason Wang
2013-09-05 0:50 ` Eric Dumazet
2013-09-05 1:23 ` Eric Dumazet
2013-09-05 3:43 ` Jason Wang
2013-09-05 3:34 ` Jason Wang
2013-09-05 3:07 ` Jason Wang
2013-09-05 3:41 ` Eric Dumazet
2013-09-05 5:16 ` Jason Wang
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