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From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: Name hashing function causing a perf regression
Date: Mon, 15 Sep 2014 17:25:16 +0100
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To: Linus Torvalds <torvalds@linux-foundation.org>
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On Mon, Sep 15, 2014 at 09:22:57AM -0700, Linus Torvalds wrote:

> The other performance issues I found are actually potentially worse,
> but they aren't regressions and they hit only when using namespaces.
> Which mostly nobody does on old kernels anyway. More of a "systemd
> uses namespaces for /tmp, and then it's quite noticeable as slowing
> down pathname lookups there if you benchmark it".

Umm...  They are easy to trigger with just mount --bind; no namespaces
needed, actually.