Messages in this thread | | | Subject | Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks | From | Ric Wheeler <> | Date | Thu, 17 Mar 2016 13:50:49 -0400 |
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On 03/17/2016 01:47 PM, Linus Torvalds wrote: > On Wed, Mar 16, 2016 at 10:18 PM, Gregory Farnum <greg@gregs42.com> wrote: >> So we've not asked for NO_HIDE_STALE on the mailing lists, but I think >> it was one of the problems Sage had using xfs in his BlueStore >> implementation and was a big part of why it moved to pure userspace. >> FileStore might use NO_HIDE_STALE in some places but it would be >> pretty limited. When it came up at Linux FAST we were discussing how >> it and similar things had been problems for us in the past and it >> would've been nice if they were upstream. > Hmm. > > So to me it really sounds like somebody should cook up a patch, but we > shouldn't put it in the upstream kernel until we get numbers and > actual "yes, we'd use this" from outside of google. > > I say "outside of google", because inside of google not only do we not > get numbers, but google can maintain their own patch. > > But maybe Ted could at least post the patch google uses, and somebody > in the Ceph community might want to at least try it out... > >> What *is* a big deal for >> FileStore (and would be easy to take advantage of) is the thematically >> similar O_NOMTIME flag, which is also about reducing metadata updates >> and got blocked on similar stupid-user grounds (although not security >> ones): http://thread.gmane.org/gmane.linux.kernel.api/10727. > Hmm. I don't hate that patch, because the NOATIME thing really does > wonders on many loads. NOMTIME makes sense. > > It's not like you can't do this with utimes() anyway. > > That said, I do wonder if people wouldn't just prefer to expand on and > improve on the lazytime. > > Is there some reason you guys didn't use that? > >> As noted though, we've basically given up and are moving to a >> pure-userspace solution as quickly as we can. > That argues against worrying about this all in the kernel unless there > are other users. > > Linus
Just a note, when Greg says "user space solution", Ceph is looking at writing directly to raw block devices which is kind of a through back to early enterprise database trends.
Ric
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