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From: Nikita Danilov <Nikita@Namesys.COM>
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Date: Thu, 20 Feb 2003 20:00:01 +0300
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To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@transmeta.com>,
       Alex Larsson <alexl@redhat.com>, <procps-list@redhat.com>
Subject: Re: [patch] procfs/procps threading performance speedup, 2.5.62
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Ingo Molnar writes:
 > 

[...]

 > 
 > to fix this overhead i've introduced a 'lookup cursor' cookie, which is
 > cached in filp->private_data, across readdir() [getdents64()] calls. If
 > the cursor matches then we skip all the overhead of skipping threads. If
 > the cursor is not available then we fall back to the old-style skipping
 > algorithm.

Shouldn't filp->private_data be cleared on lseek? It looks like lookup
cursor is never cleared once set and so readdir will always go forward
independently of ->f_pos updates. Note that glibc implementation of
readdir() (on the top of getdents64()) does call lseek on the
directory. So does seekdir(3).

 > 
 > 2) procps is forced to parse every thread in /proc to build up accurate
 >    'process CPU usage' counters. The parsing and accessing of every

Nikita.
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