linux-kernel - Re: [PATCH v2 0/4] timer: Improve itimers scalability

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Date:	Fri, 16 Oct 2015 09:12:02 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jason Low <jason.low@....com>
Cc:	Jason Low <jason.low2@...com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	George Spelvin <linux@...izon.com>, hideaki.kimura@....com,
	terry.rudd@....com, scott.norton@....com
Subject: Re: [PATCH v2 0/4] timer: Improve itimers scalability


* Jason Low <jason.low@....com> wrote:

> > > With this patch set (along with commit 1018016c706f mentioned above),
> > > the performance hit of itimers almost completely goes away on the
> > > 16 socket system.
> > > 
> > > Jason Low (4):
> > >   timer: Optimize fastpath_timer_check()
> > >   timer: Check thread timers only when there are active thread timers
> > >   timer: Convert cputimer->running to bool
> > >   timer: Reduce unnecessary sighand lock contention
> > > 
> > >  include/linux/init_task.h      |    3 +-
> > >  include/linux/sched.h          |    9 ++++--
> > >  kernel/fork.c                  |    2 +-
> > >  kernel/time/posix-cpu-timers.c |   63 ++++++++++++++++++++++++++++-----------
> > >  4 files changed, 54 insertions(+), 23 deletions(-)
> > 
> > Is there some itimers benchmark that can be used to measure the effects of these 
> > changes?
> 
> Yes, we also wrote a micro benchmark which generates cache misses and measures 
> the average cost of each cache miss (with itimers enabled). We used this while 
> writing and testing patches, since it takes a bit longer to set up and run the 
> database.

Mind posting it, so that people can stick it into a new 'perf bench timer' 
subcommand, and/or reproduce your results with it?

Thanks,

	Ingo
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