linux-kernel - Re: [PATCH] perf tools: Dont use openat()

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Date:	Thu, 24 Sep 2009 23:50:47 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ulrich Drepper <drepper@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	linux kernel <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf tools: Dont use openat()

Ulrich Drepper a écrit :
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Eric Dumazet wrote:
>>> We can certainly remove that reliance - wanna send a patch for it?
> 
> Come on, the silliness has to stop.  The kernel must be recent and to
> use it adequately the C library also must be recent.  And "recent" is
> not even correct anymore: the functions are available for more then two
> years.  Removing the use of the modern interfaces makes everything
> slower and might even re-introduce race conditions my patch fixed.
> 

First time I ear that C library *must* be recent. This was never
mentionned in Documentation/Changes, "Minimal Requirements"

"perf list" can be 100x slower, and even racy, I dont mind. At all.

$ time perf list >/dev/null 2>/dev/null

real    0m0.001s
user    0m0.000s
sys     0m0.001s

With openat(), I cannot use "perf" on machines I can only change kernel,
since changing glibc is too risky for legacy apps. I could use static and
private glibc, but last time I tried this I lost few hours and failed.

If modern interfaces means : "Upgrade glibc or die, silly you..."
I prefer to be silly, and keep increasing linux usability, even
if I dont have the chance to have a modern lab with up2date distros.

BTW, oprofile compiles perfectly on RHEL4 and 'old' glibc.

Thanks
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