From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, Jesper Dangaard Brouer <brouer@redhat.com>,
Eugenio Perez Martin <eperezma@redhat.com>
Subject: performance bug in virtio net xdp
Date: Wed, 6 May 2020 04:08:27 -0400 [thread overview]
Message-ID: <20200506035704-mutt-send-email-mst@kernel.org> (raw)
So for mergeable bufs, we use ewma machinery to guess the correct buffer
size. If we don't guess correctly, XDP has to do aggressive copies.
Problem is, xdp paths do not update the ewma at all, except
sometimes with XDP_PASS. So whatever we happen to have
before we attach XDP, will mostly stay around.
The fix is probably to update ewma unconditionally.
--
MST
next reply other threads:[~2020-05-06 8:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 8:08 Michael S. Tsirkin [this message]
2020-05-06 8:37 ` performance bug in virtio net xdp Jason Wang
2020-05-06 11:57 ` Michael S. Tsirkin
2020-05-06 8:37 ` Jesper Dangaard Brouer
2020-05-06 11:57 ` Michael S. Tsirkin
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