Re: [PATCH, v2] anon_vmas: Convert the rwsem to an rwlock_t

From: Waiman Long
Date: Mon Sep 30 2013 - 15:35:31 EST

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).


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.

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