Subject: Re: [PATCH, v2] anon_vmas: Convert the rwsem to an rwlock_t
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Waiman Long <waiman.long@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        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>, 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>
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Date: Mon, 30 Sep 2013 12:47:16 -0700
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On Mon, 2013-09-30 at 15:35 -0400, Waiman Long wrote:
> On 09/30/2013 03:23 PM, Tim Chen wrote:
> > On Mon, 2013-09-30 at 20:14 +0200, Peter Zijlstra wrote:
> >> On Mon, Sep 30, 2013 at 10:10:27AM -0700, Tim Chen wrote:
> >>> Here's the exim workload data:
> >>>
> >>> rwsem improvment:
> >>> Waimain's patch:        +2.0%
> >>> Alex+Tim's patchset:    +4.8%
> >>> Waiman+Alex+Tim:        +5.3%
> >>>
> >>> convert rwsem to rwlock_t for root anon_vma lock
> >>> Ingo's patch		+11.7%
> >>>
> >> What happens if you stuff Waiman's qrwlock patches on top of that?
> >> admittedly and oft mentioned in this thread, our current rwlock_t is
> >> somewhat suboptimal under a number of conditions.
> > I've tested with Waiman's qrwlock patches on top of Ingo's patches.
> > It does not affect the throughput for exim and I still get
> > about +11.7% throughput change (same as with Ingo's patch only).
> >
> > Tim
> >
> 
> My qrwlock doesn't enable qrwlock by default. You have to use menuconfig 
> to explicitly enable it. Have you done that when you build the test 
> kernel? I am thinking of explicitly enabling it for x86 if the anon-vma 
> lock is converted back to a rwlock.
> 

Yes, I have explicitly enabled it during my testing.

Thanks.
Tim

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