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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
