Date: Thu, 16 Sep 2010 07:59:49 -0400 From: John Baldwin <jhb@freebsd.org> To: cronfy <cronfy@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: is vfs.lookup_shared unsafe in 7.3? Message-ID: <201009160759.49179.jhb@freebsd.org> In-Reply-To: <AANLkTincNbk3wdcgRPsoeLLkKkSrFe_xcY6K-KPkGH-7@mail.gmail.com> References: <AANLkTinEje-%2B1P1n33YMKAaciaYHQH%2BdpwgX6UY1dOux@mail.gmail.com> <201009151509.49728.jhb@freebsd.org> <AANLkTincNbk3wdcgRPsoeLLkKkSrFe_xcY6K-KPkGH-7@mail.gmail.com>
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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)? Yes. -- John Baldwin
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