From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:58738 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727218AbfDYLeB (ORCPT ); Thu, 25 Apr 2019 07:34:01 -0400 Date: Thu, 25 Apr 2019 04:33:59 -0700 From: Matthew Wilcox Subject: Re: [LSF/MM TOPIC] guarantee natural alignment for kmalloc()? Message-ID: <20190425113358.GI19031@bombadil.infradead.org> References: <790b68b7-3689-0ff6-08ae-936728bc6458@suse.cz> <20190411132819.GB22763@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190411132819.GB22763@bombadil.infradead.org> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Vlastimil Babka Cc: lsf-pc@lists.linux-foundation.org, Linux-FSDevel , linux-mm , linux-block@vger.kernel.org, Michal Hocko , Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim , Ming Lei , linux-xfs@vger.kernel.org, Christoph Hellwig , Dave Chinner , "Darrick J . Wong" On Thu, Apr 11, 2019 at 06:28:19AM -0700, Matthew Wilcox wrote: > On Thu, Apr 11, 2019 at 02:52:08PM +0200, Vlastimil Babka wrote: > > In the session I hope to resolve the question whether this is indeed the > > right thing to do for all kmalloc() users, without an explicit alignment > > requests, and if it's worth the potentially worse > > performance/fragmentation it would impose on a hypothetical new slab > > implementation for which it wouldn't be optimal to split power-of-two > > sized pages into power-of-two-sized objects (or whether there are any > > other downsides). > > I think this is exactly the kind of discussion that LSFMM is for! It's > really a whole-system question; is Linux better-off having the flexibility > for allocators to return non-power-of-two aligned memory, or allowing > consumers of the kmalloc API to assume that "sufficiently large" memory > is naturally aligned. This has been scheduled for only the MM track. I think at least the filesystem people should be involved in this discussion since it's for their benefit. Do we have an lsf-discuss mailing list this year? Might be good to coordinate arrivals / departures for taxi sharing purposes.