From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754826AbbGPKNx (ORCPT ); Thu, 16 Jul 2015 06:13:53 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55721 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754024AbbGPKNv (ORCPT ); Thu, 16 Jul 2015 06:13:51 -0400 Date: Thu, 16 Jul 2015 10:55:51 +0200 From: Jan Kara To: Dave Hansen Cc: Jan Kara , Oleg Nesterov , Al Viro , Linus Torvalds , Paul McKenney , Peter Zijlstra , Daniel Wagner , Davidlohr Bueso , Ingo Molnar , Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw_semaphore Message-ID: <20150716085551.GH22847@quack.suse.cz> References: <20150713212536.GA13855@redhat.com> <20150714104810.GB24369@quack.suse.cz> <20150714133731.GA24837@redhat.com> <55A57C50.1080406@linux.intel.com> <20150714212249.GA18441@redhat.com> <55A581F9.3090507@linux.intel.com> <20150715064705.GA22609@quack.suse.cz> <20150715181920.GA1797@redhat.com> <20150716072654.GE22847@quack.suse.cz> <55A75D93.1090105@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55A75D93.1090105@linux.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 16-07-15 00:30:27, Dave Hansen wrote: > On 07/16/2015 12:26 AM, Jan Kara wrote: > > So Dave's patches would go in only in the next merge window anyway so we > > still have like two-three weeks to decide which patchset to take. If you > > think it will take you longer, then merging Dave's patches makes some sense > > although I personally don't think the issue is so important that we have to > > fix it ASAP and eventual delay of one more release would be OK for me. > > I thought of one more thing. > > Oleg's patches are fast in the uncontended case. My testing of his code > so far was all single-threaded. Will it slow down if we throw a bunch > of threads at it an see contention? I don't think my RCU approach will. > > I can benchmark in the next few days on a larger machine. Well, his semaphore is percpu as well so I don't think there should be a difference (there may be some difference when freeze is in progress but that doesn't really matter). But it's always good to verify. Honza -- Jan Kara SUSE Labs, CR