Date: Wed, 20 Apr 2005 11:20:38 -0400 From: Brian Fundakowski Feldman <green@freebsd.org> To: Marc Olzheim <marcolz@stack.nl> Cc: freebsd-current@freebsd.org Subject: Re: NFS client/buffer cache deadlock Message-ID: <20050420152038.GI1157@green.homeunix.org> In-Reply-To: <20050420143842.GB77731@stack.nl> References: <20050418203321.GA88774@stack.nl> <20050419133227.GA11612@stack.nl> <20050419151800.GE1157@green.homeunix.org> <20050419160258.GA12287@stack.nl> <20050419160900.GB12287@stack.nl> <20050419161616.GF1157@green.homeunix.org> <20050419204723.GG1157@green.homeunix.org> <20050420140409.GA77731@stack.nl> <20050420142448.GH1157@green.homeunix.org> <20050420143842.GB77731@stack.nl>
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On Wed, Apr 20, 2005 at 04:38:42PM +0200, Marc Olzheim wrote: > On Wed, Apr 20, 2005 at 10:24:48AM -0400, Brian Fundakowski Feldman wrote: > > > It does and it seems to work. The NFS performance drops considerably > > > though, from 8/9 MByte/s to 3/4 on sequential reads for instance. > > > > > > kern/79208 is fixed by this indeed, in that I get short writes (in case > > > of my test server at 1802240+ bytes, so './writev 2 foo' fails... > > > > Performance drops in what cases? > > Hmm, seems only to happen in large sequential reads... It might just be > the FreeBSD 4.6 NFS server that is the problem though. I've had more NFS > troubles with it. Reads should be totally unaffected... > Btw.: I'm not sure write(),writev() and pwrite() are allowed to do short > writes on regular files... ? Our manpage is incorrect; POSIX states that they are (see earlier e-mail). There really is no alternative -- we simply can't build an NFS transaction larger than our buffer cache can accomodate. Note that short wries won't happen for normal buffer sizes, only excessively large ones. I really don't believe that writev() is meant to be used so that you can write gigantic data structures in a single transaction... -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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