linux-kernel - Re: spinlocks -- why are releases inlined and acquires are not?

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Message-ID: <Pine.LNX.4.64.0804011043540.5541@jikos.suse.cz>
Date:	Tue, 1 Apr 2008 10:44:50 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Ingo Molnar <mingo@...e.hu>
cc:	linux-kernel@...r.kernel.org
Subject: Re: spinlocks -- why are releases inlined and acquires are not?

On Tue, 1 Apr 2008, Ingo Molnar wrote:

> > In fact we have received report from one of our users that he is 
> > seeing approximately 15% performance degradation of mmap() when 
> > spinlocks are not inlined. I am going to do some performance 
> > measurements myself shortly, as it seems quite strange, but while at 
> > it, I have noticed the aforementioned asymetry in spinlock.h, so I 
> > just wanted to know if there is any particular reason behind that.
> inlining decisions almost never have effects of that order of magnitude 
> - especially on new CPUs, so that 15% looks quite suspicious to me. 

Definitely, that's why I am a little bit suspicious. Thanks,

-- 
Jiri Kosina
SUSE Labs
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