From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754091AbbG0UbR (ORCPT ); Mon, 27 Jul 2015 16:31:17 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:44327 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750915AbbG0UbP (ORCPT ); Mon, 27 Jul 2015 16:31:15 -0400 Date: Mon, 27 Jul 2015 13:31:10 -0700 From: josh@joshtriplett.org To: Davidlohr Bueso Cc: Andrew Morton , "Paul E. McKenney" , Stephen Rothwell , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: linux-next: build failure after merge of the akpm-current tree Message-ID: <20150727203110.GB28119@cloud> References: <20150724153334.543cfc7b@canb.auug.org.au> <1437768965.3298.52.camel@stgolabs.net> <20150724230902.GQ3717@linux.vnet.ibm.com> <20150725194739.GA9753@x> <1437859442.3298.68.camel@stgolabs.net> <20150725223524.GA14593@x> <20150727130312.d87e352473dfd8b431c8c07b@linux-foundation.org> <1438028402.25997.58.camel@stgolabs.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438028402.25997.58.camel@stgolabs.net> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 27, 2015 at 01:20:02PM -0700, Davidlohr Bueso wrote: > On Mon, 2015-07-27 at 13:03 -0700, Andrew Morton wrote: > > On Sat, 25 Jul 2015 15:35:24 -0700 Josh Triplett wrote: > > > > > > Some mm functionality might very possibly rely on srcu in the future if > > > > we expect any chances of scaling, ie: faults. So I'd rather not take a > > > > short term solution here, as we'll probably be discussing this again > > > > otherwise. > > > > > > What other mm functionality plans to use SRCU? > > Right now I have (unpublished) patches that use srcu as a way to avoid > mmap_sem when faulting across the entire path. Previous alternatives > also use it, as ie, can involve IO and lots of other sleeping > operations. That sounds interesting! mmap_sem is definitely a performance bottleneck. How do you handle writes versus reads? > Yes, you can argue that they're not published all you want, > but I'm talking beyond my specific use case. Linux VM is known to scale, > why should we hide a core scalability tool from it? In the case of mmap_sem, does it help at all if tiny kernels were 1) non-preemptible and 2) non-SMP? Tiny kernels don't necessarily care about scaling. > > > Among other things, no-mmu builds might still be able to omit it. > > > > Yup. > > Makes sense. Thanks. - Josh Triplett