On Thu, 2014-07-10 at 18:25 +1000, NeilBrown wrote: > On Thu, 10 Jul 2014 15:43:40 +0800 Ian Kent <raven@xxxxxxxxxx> wrote: > > > On Thu, 2014-07-10 at 09:41 +1000, NeilBrown wrote: > > > autofs4 currently doesn't support RCU-walk - it immediately > > > aborts any attempt at RCU-walk to force REF-walk for path name > > > lookup. > > > > > > This can cause a significant performance impact on multi-core > > > systems. > > > I have a client with a test case which spends >80% of its time > > > waiting for spinlocks with a "make -j 40" on a 40 core system. > > > > Right, sounds worth the effort. > > > > > > > > This patchset aims to remove most of these spinlocks. To be fully > > > effective in the particular case it needs a second patch set which > > > makes NFS RCU-walk friendly, but one thing at a time. > > > > > > This has only been lightly tested so far so I'm really after feed-back > > > rather than to have the patch set accepted, though the first two > > > patches are trivial and could be taken immediately. > > > > I've only scanned the patches so far, I'll need to spend a bit more time > > on them before I can comment. > > > > I'm going to be pressed for time for at least several days so I won't be > > able to get to this right away. > > > > I expect the submount_test I use to stress path walking and expire to > > mount transitions will likely be a good test to use. I haven't used it > > in my personal environment for quite a while now so I'll need to have a > > look around and see if I can still find a suitable set of scripts. > > Otherwise I'll need to decouple it from the RedHat automated test > > environment. > > > > > > > > The last two patches are the most interesting so review comments on > > > those are particularly welcome. > > > > Again I haven't looked closely at these but don't you mean the last > > three patches or am I just fussing over an obviously straight forward > > patch 3? > > Exactly right - that thirds last patch was "obviously straight forward", so > is naturally the one that I have already found a bug in (the patch assumes > that autofs4_check_leaves returns a different dentry, which clearly isn't > true). Ha, IIRC that was to support the old pseudo direct mounts that would expire the leaves of a tree independently. That was a long time ago now and probably isn't used but it should remain think. I'll need to have a look at that too, to refresh my memory. > > I'll repost it, probably on Monday. > > > > > Thanks for your effort Bruce, > > Ian > > > > http://www.youtube.com/watch?v=_f_p0CgPeyA > > (Usually when people get my name wrong they call me "Ian", so you calling me > Bruce is both slightly ironic and quite refreshing!) LOL, but I have a lame excuse! I was thinking Bruce Fields when replying since have the impression you both work in similar areas. Ian -- To unsubscribe from this list: send the line "unsubscribe autofs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
