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Message-ID: <Pine.LNX.4.64.0705121120210.26287@frodo.shire>
Date: Sat, 12 May 2007 11:27:13 +0200 (CEST)
From: Esben Nielsen <nielsen.esben@...glemail.com>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Oleg Nesterov <oleg@...sign.ru>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex
On Fri, 11 May 2007, Peter Zijlstra wrote:
>
> I was toying with a scalable rw_mutex and found that it gives ~10% reduction in
> system time on ebizzy runs (without the MADV_FREE patch).
>
You break priority enheritance on user space futexes! :-(
The problems is that the futex waiter have to take the mmap_sem. And as
your rw_mutex isn't PI enabled you get priority inversions :-(
Esben
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