Date: Mon, 30 Sep 2013 12:46:58 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>, Waiman Long <Waiman.Long@hp.com>,
        Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rik van Riel <riel@redhat.com>,
        Peter Hurley <peter@hurleysoftware.com>,
        Davidlohr Bueso <davidlohr.bueso@hp.com>,
        Alex Shi <alex.shi@intel.com>, Tim Chen <tim.c.chen@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Matthew R Wilcox <matthew.r.wilcox@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Michel Lespinasse <walken@google.com>,
        Andi Kleen <andi@firstfloor.org>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        "Norton, Scott J" <scott.norton@hp.com>
Subject: Re: [PATCH] rwsem: reduce spinlock contention in wakeup code path
Message-ID: <20130930104658.GX3081@twins.programming.kicks-ass.net>
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On Sat, Sep 28, 2013 at 11:55:26AM -0700, Linus Torvalds wrote:
> So if the primary reason for this is really just that f*cking anon_vma
> lock, then I would seriously suggest:

I would still like to see the rwsem patches merged; even if we end up
going back to a spin style anon_vma lock.

There's been various reports in the past about how programs are
significantly faster if they wrap their mmap() calls in a pthread_mutex.
And this was purely down to the fact that rwsem writer-writer contention
blows chunks.
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