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Date: Fri, 16 Oct 2015 09:12:02 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Jason Low <jason.low@hpe.com>
Cc: Jason Low <jason.low2@hp.com>, Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
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        George Spelvin <linux@horizon.com>, hideaki.kimura@hpe.com,
        terry.rudd@hpe.com, scott.norton@hpe.com
Subject: Re: [PATCH v2 0/4] timer: Improve itimers scalability
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* Jason Low <jason.low@hpe.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