From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 03/13] scsi: unify allocation of scsi command and sense buffer Date: Mon, 25 May 2009 09:46:47 +0200 Message-ID: <20090525074647.GK11363@kernel.dk> References: <1243236668-3398-1-git-send-email-jens.axboe@oracle.com> <1243236668-3398-6-git-send-email-jens.axboe@oracle.com> <20090525074124.GA31746@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, chris.mason@oracle.com, david@fromorbit.com, akpm@linux-foundation.org, jack@suse.cz, yanmin_zhang@linux.intel.com, linux-scsi@vger.kernel.org To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20090525074124.GA31746@infradead.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, May 25 2009, Christoph Hellwig wrote: > On Mon, May 25, 2009 at 09:30:48AM +0200, Jens Axboe wrote: > > Fold the sense buffer into the command, thereby eliminating a slab > > allocation and free per command. > > Might help to send it to linux-scsi to get people to review and apply it > :) yeah, as I later posted, this wasn't meant to be sent out as part of the writeback series :-) > But that patch looks good to me, avoiding one allocation for each > command and simplifying the code. I try to remember why these were > two slabs to start with but can't find any reason. > > Btw, we might just want to declare the sense buffer directly as a sized > array in the scsi command as there really doesn't seem to be a reason > not to allocate it. That is also a workable solution. I've been trying to cut down on the number of allocations required per-IO, and there's definitely still some low hanging fruit there. Some of it is already included, like the inline io_vecs in the bio. -- Jens Axboe