lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 6 May 2020 04:08:27 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eugenio Perez Martin <eperezma@...hat.com>
Subject: performance bug in virtio net xdp

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

Powered by blists - more mailing lists