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  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Wed, 27 Aug 2014 06:23:58 -0700
From:	Eric Dumazet <>
To:	Hannes Frederic Sowa <>
Cc:	David Miller <>,,,,,,,,
Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush

On Wed, 2014-08-27 at 14:31 +0200, Hannes Frederic Sowa wrote:

> One thing one should keep in mind is, that there must be a skb available
> to trigger the flush, maybe this will hurt us one day.
> Thinking more about it should we go with a coccinelle script and
> replace/extend ndo_start_xmit with an additional argument?

This will be a pain for backports and things like that.

skb->xmit_more is a bit annoying, because it consumes one bit in all
skbs, while it could be one byte per cpu as ndo_start_xmit() is called
while BH are disabled.

It also forces a cache line dirtying, that will hurt qdisc like HTB
where skbs can be cooked/enqueued by remote cpus.

Also, most drivers will never benefit from this new infra.

Mellanox mlx4 uses the Blue Frame trick to avoid the iowrite() cost.

I am afraid Jesper tests are not complete to truly have a picture of the
extra costs, because he made sure no false sharing was possible (A
single cpu does everything and keeps skb in its cache)

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists