From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423451Ab3FUXv3 (ORCPT ); Fri, 21 Jun 2013 19:51:29 -0400 Received: from mga02.intel.com ([134.134.136.20]:21580 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423151Ab3FUXv2 (ORCPT ); Fri, 21 Jun 2013 19:51:28 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,916,1363158000"; d="scan'208";a="357646156" Subject: [PATCH 0/2] rwsem: performance enhancements for systems with many cores From: Tim Chen To: Ingo Molnar , Andrew Morton Cc: Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Peter Zijlstra , Rik van Riel , Tim Chen , linux-kernel@vger.kernel.org, linux-mm Content-Type: text/plain; charset="UTF-8" Date: Fri, 21 Jun 2013 16:51:31 -0700 Message-ID: <1371858691.22432.3.camel@schen9-DESK> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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