From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754688Ab3BFAHG (ORCPT ); Tue, 5 Feb 2013 19:07:06 -0500 Received: from mga01.intel.com ([192.55.52.88]:35537 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257Ab3BFAHE (ORCPT ); Tue, 5 Feb 2013 19:07:04 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,610,1355126400"; d="scan'208";a="287088112" Message-ID: <51119ED0.3030207@intel.com> Date: Wed, 06 Feb 2013 08:07:44 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Ingo Molnar CC: torvalds@linux-foundation.org, paul.gortmaker@windriver.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rwsem: steal writing sem for better performance References: <1360069915-31619-1-git-send-email-alex.shi@intel.com> <20130205145854.GA30949@gmail.com> In-Reply-To: <20130205145854.GA30949@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/05/2013 10:58 PM, Ingo Molnar wrote: > > * Alex Shi wrote: > >> Commit 5a50508 change to rwsem from mutex, that cause aim7 fork_test >> dropped 50%. Yuanhan liu does a good analysis, find it caused by >> strict sequential writing. Ingo suggest stealing sem writing from >> front task in waiting queue. https://lkml.org/lkml/2013/1/29/84 >> So has this patch. >> >> In this patch, I just allow writing steal happen when the >> first waiter is also writer. Then the performance fully >> recovered. > > All the aim7 fork_test performance regression is recovered? Sure. 100% recovered on my NHM EP, NHM EX, SNB EP 2S and 4S machines. > > Thanks, > > Ingo > -- Thanks Alex