linux-kernel - Re: [PATCH][RESEND] Export per-tid and per-tgid cputime in nanoseconds.

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Message-ID: <1267466740.1579.36.camel@laptop>
Date:	Mon, 01 Mar 2010 19:05:40 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Divyesh Shah <dpshah@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, kenchen@...gle.com
Subject: Re: [PATCH][RESEND] Export per-tid and per-tgid cputime in 
 nanoseconds.

On Mon, 2010-03-01 at 07:44 -0800, Divyesh Shah wrote:
> On Sat, Feb 27, 2010 at 3:43 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Fri, 2010-02-26 at 18:03 -0800, Divyesh Shah wrote:
> > > This can be used by applications to get finer granularity cputime usage on
> > > platforms that use timestamp counters or HPET.
> >
> > I guess the patch looks good, I'm just not sure what HPET got to do with
> > anything.. the scheduler certainly doesn't use HPET for timekeeping, its
> > terribly slow to read.
> 
> Yes you're right. Please ignore the HPET comment.
> 
> >
> > Also, it would be good to get some more justification than 'some
> > applications can use this', which is basically a truism for any patch
> > that adds a user interface.
> 
> 1) This should be useful for a shared or virtualized environment where
> the shared management infrastructure needs to charge each application
> as accurately as possible for cpu usage.
> 2) An application that services different users and does some
> cpu-intensive work may want to measure cpu time spent for each user by
> the serving thread.
> 
> I think applications like web servers, remote database servers, etc.
> fit into the second category.
> 
> For units of work smaller than a jiffy, this really helps as some
> threads could potentially hide from the jiffy based accounting.
> 
> Please let me know if you want me to send the patch again with the
> corrected description and added justification.


Its all should and may, anything concrete?

Also, doesn't muck like schedstat, task_delay_accounting, cpuacct-cgroup
or some other stuff expose this number already?

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