is vfs.lookup_shared unsafe in 7.3?
jhb at freebsd.org
Thu Sep 16 11:59:52 UTC 2010
On Thursday, September 16, 2010 3:53:47 am cronfy wrote:
> >> Hello,
> >> Trying to overtake high server load (sudden peaks of 15%us/85%sy, LA >
> >> 40, very slow lstat() at these moments, looks like some kind of lock
> >> contention) I enabled vfs.lookup_shared=1 on two servers today. One is
> >> FreeBSD-7.3 kernel csup'ed and built Sep 9 2010 and other is
> >> FreeBSD-7.3 csup'ed and built Jul 16 2010.
> >> The server with more fresh kernel is running nice and does not show
> >> high load anymore. But on the second server it did not help. More,
> >> after a few hours of work with vfs.lookup_shared=1 I noticed processes
> >> stucked in "ufs" state. I tried to kill them with no luck. Disabling
> >> vfs.lookup_shared freezed the whole system.
> >> So, is vfs.lookup_shared=1 unsafe in 7.3? Did it become more stable
> >> between 16 Jul and 9 Sep (is it the reason why first system is still
> >> running?), or should I expect that it will freeze in a near time too?
> >> Thanks in advance!
> > No, 7.3 has a bug that can cause these hangs that is probably made worse by
> > vfs.lookup_shared=1, but can occur even if it is disabled. You want
> > these fixes applied (in order, one of them reverts part of another):
> Thank you for the fix and for the explanation, that's exactly what I
> wanted to know. Just to be sure: do these patches completely fix the
> bug with hangs (even without vfs.lookup_shared=1)?
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