netdev - Re: [PATCH net-next] sock: don't enable netstamp for af

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 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]

Message-Id: <1445944516.1337466.421368457.2463FECE@webmail.messagingengine.com>
Date:	Tue, 27 Oct 2015 12:15:16 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH net-next] sock: don't enable netstamp for af_unix sockets



On Tue, Oct 27, 2015, at 12:09, Hannes Frederic Sowa wrote:
> Hi Richard,
> 
> On Tue, Oct 27, 2015, at 11:11, Richard Cochran wrote:
> > On Mon, Oct 26, 2015 at 02:32:59PM +0100, Hannes Frederic Sowa wrote:
> > > On Mon, Oct 26, 2015, at 14:19, Richard Cochran wrote:
> > > > On Mon, Oct 26, 2015 at 01:51:37PM +0100, Hannes Frederic Sowa wrote:
> > > > > netstamp_needed is toggled for all socket families if they request
> > > > > timestamping. But some protocols don't need the lower-layer timestamping
> > > > > code at all. This patch starts disabling it for af-unix.
> > > > 
> > > > What problem is this patch trying to solve?
> > > 
> > > netstamp_needed is a static-key which enables timestamping code in the
> > > networking stack receive functions for every packet, while it is not
> > > needed for AF_UNIX/LOCAL. So it is merely a small performance
> > > enhancement.
> > 
> > Are there any numbers that show the effect of this enhancement?
> 
> I haven't personally done any performance numbers.
> 
> Jesper (in Cc) noticed that it showed up in perf performance reports
> even though he used a very minimal setup. Turned out that
> systemd-journald enables timestamping on AF_UNIX sockets which thus
> enabled netstamps globally. I think Jesper can chime in here.

Also counter question: why is the netstamp code protected by a
static_key otherwise if not for trying to suppress the code path as
often as possible if not used? ;)

Bye,
Hannes
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html