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Message-ID: <1371858691.22432.3.camel@schen9-DESK>
Date: Fri, 21 Jun 2013 16:51:31 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Alex Shi <alex.shi@...el.com>,
Andi Kleen <andi@...stfloor.org>,
Michel Lespinasse <walken@...gle.com>,
Davidlohr Bueso <davidlohr.bueso@...com>,
Matthew R Wilcox <matthew.r.wilcox@...el.com>,
Dave Hansen <dave.hansen@...el.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Rik van Riel <riel@...hat.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: [PATCH 0/2] rwsem: performance enhancements for systems with many
cores
In this patchset, we introduce two optimizations to read write semaphore.
The first one reduces cache bouncing of the sem->count field
by doing a pre-read of the sem->count and avoid cmpxchg if possible.
The second patch introduces similar optimistic spining logic in
the mutex code for the writer lock acquisition of rw-sem.
Combining the two patches, in testing by Davidlohr Bueso on aim7 workloads
on 8 socket 80 cores system, he saw improvements of
alltests (+14.5%), custom (+17%), disk (+11%), high_systime
(+5%), shared (+15%) and short (+4%), most of them after around 500
users when i_mmap was implemented as rwsem.
Feedbacks on the effectiveness of these tweaks on other workloads
will be appreciated.
Alex Shi (1):
rwsem: check the lock before cpmxchg in down_write_trylock and
rwsem_do_wake
Tim Chen (1):
rwsem: do optimistic spinning for writer lock acquisition
Makefile | 2 +-
include/asm-generic/rwsem.h | 8 +-
include/linux/rwsem.h | 3 +
init/Kconfig | 9 +++
kernel/rwsem.c | 29 +++++++-
lib/rwsem.c | 169 ++++++++++++++++++++++++++++++++++++++-----
6 files changed, 195 insertions(+), 25 deletions(-)
--
1.7.4.4
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