From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kent Overstreet Subject: Re: [PATCH 00/13] convert block layer to bioset_init()/mempool_init() Date: Mon, 21 May 2018 19:38:55 -0400 Message-ID: <20180521233855.GI11495@kmo-pixel> References: <2bbeeb1a-8b99-b06a-eb9b-eb8523c16460@kernel.dk> <20180521144703.GA19303@redhat.com> <4b343aef-e11c-73ba-1d88-7e73ca838cad@kernel.dk> <20180521150439.GA19379@redhat.com> <61e30dcf-a01c-f47d-087a-12930caf9aef@kernel.dk> <20180521151817.GA19454@redhat.com> <20180521160907.GA19553@redhat.com> <20180521173724.GG11495@kmo-pixel> <20180521182427.GA20013@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180521182427.GA20013@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Mike Snitzer Cc: Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, hch@infradead.org, colyli@suse.de, darrick.wong@oracle.com, clm@fb.com, bacik@fb.com, linux-xfs@vger.kernel.org, drbd-dev@lists.linbit.com, linux-btrfs@vger.kernel.org, linux-raid@vger.kernel.org, neilb@suse.com List-Id: linux-raid.ids On Mon, May 21, 2018 at 02:24:32PM -0400, Mike Snitzer wrote: > Every single data structure change in this series should be reviewed for > unforeseen alignment consequences. Jens seemed to say that is > worthwhile. Not sure if he'll do it or we divide it up. If we divide > it up a temp topic branch should be published for others to inspect. > > Could be alignment hasn't been a historic concern for a bunch of the > data structures changed in this series.. if so then all we can do is fix > up any obvious potential for false sharing. Honestly, I almost never worry about alignment... the very few times I do care, I use __cacheline_aligned_in_smp. If alignment is a concern in any of those structs, there really ought to be a comment indicating it. I very much doubt anything I touched was performance sensitive enough for it to be an issue, though. And if there is a performance impact, it should be oughtweighed by the reduced pointer chasing. If you disagree, I don't mind leaving the device mapper patch out, it really makes no difference to me. I could glance over for alignment issues but I feel like my analysis would not be terribly valuable to you considering I've already said my position on alignment is "meh, don't care" :)