Date: Sat, 20 Mar 2010 07:32:27 -0800 From: "K. Macy" <kmacy@freebsd.org> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r205132 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <82c4140e1003200832h116dee34p56022c100ff65b74@mail.gmail.com> In-Reply-To: <20100320111013.GE1733@garage.freebsd.pl> References: <201003132141.o2DLfroC041203@svn.freebsd.org> <20100320111013.GE1733@garage.freebsd.pl>
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On Sat, Mar 20, 2010 at 3:10 AM, Pawel Jakub Dawidek <pjd@freebsd.org> wrote: > On Sat, Mar 13, 2010 at 09:41:53PM +0000, Kip Macy wrote: >> Author: kmacy >> Date: Sat Mar 13 21:41:52 2010 >> New Revision: 205132 >> URL: http://svn.freebsd.org/changeset/base/205132 >> >> Log: >> Don't bottleneck on acquiring the stream locks - this avoids a massive >> drop off in throughput with large numbers of simultaneous reads > > This is another[1] change we agreed (I hoped) to properly evaluate first > through zfs-code@opensolaris.org. > Hi pjd - I ran it by zfs-code@ a year ago. I never got any meaningful feedback. I'm not being flippant when I say that I would like you to interact with them. One thing you need to also bear in mind is that Opensolaris != FreeBSD. I don't mean that in the phk "this is the wrong mailing list" sense, but rather the two have different behavioral properties. The deadlock that I had to track down by hand because you had disabled witness on ZFS locks occurred within 10 minutes on a modest web serving load and within 2 minutes under fsstress. It had been in ZFS quite some time when they finally patched it and yet it was a very serious problem on FreeBSD. Web serving throughput would drop from 2.5Gbps to a few hundred megabits per second without this change. I can only guess that sx locks do not behave the same as Solaris' mutexes to such a large extent that we get very different behaviors and you'll have to keep an open mind to local changes that cope with that fact. Thanks, Kiphome | help
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