Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932337AbaLIPtF (ORCPT ); Tue, 9 Dec 2014 10:49:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932291AbaLIPtD (ORCPT ); Tue, 9 Dec 2014 10:49:03 -0500 Date: Tue, 9 Dec 2014 10:48:59 -0500 From: Mike Snitzer To: Akira Hayakawa Cc: device-mapper development , gregkh@linuxfoundation.org, agk@redhat.com, linux-kernel@vger.kernel.org, ejt@redhat.com Subject: Re: staging: writeboost: Add dm-writeboost Message-ID: <20141209154859.GC26238@redhat.com> References: <5484498E.4000202@gmail.com> <20141207200834.GA2322@kroah.com> <5484C0E9.3060707@gmail.com> <20141209151253.GA17660@debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141209151253.GA17660@debian> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 09 2014 at 10:12am -0500, Joe Thornber wrote: > On Mon, Dec 08, 2014 at 06:04:41AM +0900, Akira Hayakawa wrote: > > Mike and Alasdair, > > I need your ack > > Hi Akira, > > I just spent some time playing with your latest code. On the positive > side I am seeing some good performance with the fio tests. Which is > great, we know your design should outperform dm-cache with small > random io. > > However I'm still getting v. poor results with the git-extract test, > which clones a linux kernel repo, and then checks out 5 revisions, all > with drop_caches in between. Thanks for re-evaluating dm-writeboost performance Joe. > It's fine to have different benefits of the caching software depending > on the load. But I think the worst case should always be close to the > performance of the raw spindle device. > > If you get the following work items done I will ack to go upstream: > > i) Get this test so it's performance is similar to raw spindle. > > ii) Write good documentation in Documentation/device-mapper/. eg. How > do I remove a cache? When should I use dm-writeboost rather than > bcache or dm-cache? > > iii) Provide an equivalent to the fsck tool to repair a damaged cache. I agree with this TODO list. But I'd also add: iv) perform full code review to catch various implementation issues, any style nits, etc. v) explore/implement read caching support (could the lack of read caching be contributing to why the git_extract test is so poor?) Item iv) would be a task for myself and anyone else interested in getting dm-writeboost ready for inclusion. Akira, I can start working on dm-writeboost code review once I complete review of the dm-dedup target (my current priority) -- but realistically that likely won't be until the new year. BTW, I'm really not seeing much point putting dm-writeboost in staging. I'd be happy to take dm-writeboost into drivers/md/ once the above list is resolved. BUT if you'd still like dm-writeboost to go into staging _without_ any of these 5 work items being completed I'll ack it but to be very clear: dm-writeboost will not migrate out of staging until these items are resolved. Thanks, Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/