Date: Wed, 10 Oct 2012 08:08:44 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: Garrett Wollman <wollman@bimajority.org> Cc: Nikolay Denev <ndenev@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: NFS server bottlenecks Message-ID: <461825404.1975816.1349870924809.JavaMail.root@erie.cs.uoguelph.ca> In-Reply-To: <20596.52616.867711.175010@hergotha.csail.mit.edu>
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Garrett Wollman wrote: > <<On Tue, 9 Oct 2012 20:18:00 -0400 (EDT), Rick Macklem > <rmacklem@uoguelph.ca> said: > > > And, although this experiment seems useful for testing patches that > > try > > and reduce DRC CPU overheads, most "real" NFS servers will be doing > > disk > > I/O. > > We don't always have control over what the user does. I think the > worst-case for my users involves a third-party program (that they're > not willing to modify) that does line-buffered writes in append mode. > This uses nearly all of the CPU on per-RPC overhead (each write is > three RPCs: GETATTR, WRITE, COMMIT). > Yes. My comment was simply meant to imply that his testing isn't a realistic load for most NFS servers. It was not meant to imply that reducing the CPU overhead/lock contention of the DRC is a useless exercise. rick > -GAWollman
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