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Date: Fri, 23 Jun 2006 14:19:26 -0700
From: Andrew Morton <akpm@osdl.org>
To: Shailabh Nagar <nagar@watson.ibm.com>
Cc: jlan@engr.sgi.com, balbir@in.ibm.com, csturtiv@sgi.com,
       linux-kernel@vger.kernel.org
Subject: Re: [Patch][RFC]  Disabling per-tgid stats on task exit in
 taskstats
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On Fri, 23 Jun 2006 13:14:41 -0400
Shailabh Nagar <nagar@watson.ibm.com> wrote:

> The results show that differential between tgid on and off
> starts becoming significant once the exit rate crosses roughly 1000
> threads/second. Below that exit rate, the difference is negligible.
> Above it, the difference starts climbing rapidly.
> 
> So I guess the question is whether this rate of exit is representative
> enough of real life to warrant making any more changes to the existing
> patchset, beyond the locking changes in 2. above.
> 
> >From my limited experience, I think this is too high an exit rate
> to be worrying about overhead.
> 

1000/sec isn't terribly high.  CGI servers, shell scripts.

And kernel development ;) A `pushpatch 1500' here does 992 fork/exec/exit
per second.

>         %ovhd of tgid on over off
>         (higher is worse)
> 
> Exit     User     Sys     Elapsed
> Rate     Time     Time    Time
> 
> 2283      25.76  649.41   -0.14
> 1193     -10.53   88.81   -0.12
> 963      -11.90    3.28   -0.10
> 806       -8.54   -0.84    0.16
> 694       -4.41    2.38    0.03

Oh wow.  Something's gone quadratic there.