From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH net-next] sock: don't enable netstamp for af_unix sockets Date: Tue, 27 Oct 2015 12:09:21 +0100 Message-ID: <1445944161.1336457.421364569.5449BCCB@webmail.messagingengine.com> References: <1445863897-22646-1-git-send-email-hannes@stressinduktion.org> <20151026131928.GA1820@netboy> <1445866379.133031.420389177.3AE9E175@webmail.messagingengine.com> <20151027101157.GA1850@netboy> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Jesper Dangaard Brouer To: Richard Cochran Return-path: Received: from out4-smtp.messagingengine.com ([66.111.4.28]:56986 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752996AbbJ0LJW (ORCPT ); Tue, 27 Oct 2015 07:09:22 -0400 Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailout.nyi.internal (Postfix) with ESMTP id CF75B20844 for ; Tue, 27 Oct 2015 07:09:21 -0400 (EDT) In-Reply-To: <20151027101157.GA1850@netboy> Sender: netdev-owner@vger.kernel.org List-ID: 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. Bye, Hannes