From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Date: Mon, 21 May 2018 19:38:55 -0400 From: Kent Overstreet 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 Subject: Re: [PATCH 00/13] convert block layer to bioset_init()/mempool_init() 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 In-Reply-To: <20180521182427.GA20013@redhat.com> List-ID: 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" :) From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f68.google.com (mail-wm0-f68.google.com [74.125.82.68]) by mail09.linbit.com (LINBIT Mail Daemon) with ESMTP id 3FD4E1005435 for ; Wed, 23 May 2018 15:40:53 +0200 (CEST) Received: by mail-wm0-f68.google.com with SMTP id t11-v6so9174505wmt.0 for ; Wed, 23 May 2018 06:40:53 -0700 (PDT) Received: from soda.linbit ([86.59.100.100]) by smtp.gmail.com with ESMTPSA id f11-v6sm10471744edf.68.2018.05.23.06.40.51 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 23 May 2018 06:40:51 -0700 (PDT) Resent-Message-ID: <20180523134050.GW499@soda.linbit> Received: from mail-qt0-f193.google.com (mail-qt0-f193.google.com [209.85.216.193]) by mail09.linbit.com (LINBIT Mail Daemon) with ESMTP id D4299101AC56 for ; Tue, 22 May 2018 01:39:00 +0200 (CEST) Received: by mail-qt0-f193.google.com with SMTP id c2-v6so21169062qtn.9 for ; Mon, 21 May 2018 16:39:00 -0700 (PDT) Date: Mon, 21 May 2018 19:38:55 -0400 From: Kent Overstreet To: Mike Snitzer 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 Content-Disposition: inline In-Reply-To: <20180521182427.GA20013@redhat.com> Cc: Jens Axboe , hch@infradead.org, linux-raid@vger.kernel.org, darrick.wong@oracle.com, linux-kernel@vger.kernel.org, colyli@suse.de, linux-block@vger.kernel.org, clm@fb.com, neilb@suse.com, bacik@fb.com, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, drbd-dev@lists.linbit.com Subject: Re: [Drbd-dev] [PATCH 00/13] convert block layer to bioset_init()/mempool_init() List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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" :)