Messages in this thread | | | Date | Tue, 9 Dec 2014 10:48:59 -0500 | From | Mike Snitzer <> | Subject | Re: staging: writeboost: Add dm-writeboost |
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On Tue, Dec 09 2014 at 10:12am -0500, Joe Thornber <thornber@redhat.com> 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
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