Date: Mon, 18 Jan 2010 12:20:07 -0800 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: freebsd-stable@freebsd.org Subject: Re: immense delayed write to file system (ZFS and UFS2), performance issues Message-ID: <20100118202007.GA54223@icarus.home.lan> In-Reply-To: <4B54C100.9080906@mail.zedat.fu-berlin.de> References: <4B54C100.9080906@mail.zedat.fu-berlin.de>
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On Mon, Jan 18, 2010 at 09:13:52PM +0100, O. Hartmann wrote: > I realise a strange behaviour of several FreeBSD 8.0-STABLE/amd64 > boxes. All boxes have the most recent STABLE. One box is a UP > system, two others SMP boxes, one with a Q6600 4-core, another XEON > with 2x 4-cores (Dell Poweredge III). > > Symptome: All boxes have ZFS and UFS2 filesystems. Since two weeks > or so, sometimes the I/O performance drops massively when doing 'svn > update', 'make world' or even 'make kernel'. It doesn't matter what > memory and how many cpu the box has, it get stuck for several > seconds and freezing. On the UP box, this is sometimes for 10 - 20 > seconds. > A very interesting phenomenon is the massively delayed file writing > on ZFS filesystems I realise. Editing a file in 'vi' running on one > XTerm and having in another Xterminal my shell for compiling this > file, it takes sometimes up to 20 seconds to get the file updated > after it has been written. It's like having an old, slow NFS > connection with long cache delays. > These massively delayed file transactions are not necessarely under > heavy load, sometimes they occur in a relaxed situation. They seem > to occur much more often on the UP box than on the SMP boxes, but > this strange phenomenon also occur on the Dell Poweredge II, which > has 16GB RAM and summa summarum 16 cores. This phenomenon does occur > on ZFS- and UFS2 filesystems as well. It is hardly reproducable. Possibly this is an extreme example of what Garrett Moore et al have been discussing recently? http://lists.freebsd.org/pipermail/freebsd-stable/2010-January/053845.html You might try the force-swap-out approach here to find out if what you're seeing is identical: http://lists.freebsd.org/pipermail/freebsd-stable/2010-January/053949.html -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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