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Date: Sat, 25 Jan 2014 22:13:14 -0500
From: Garrett Wollman <wollman@freebsd.org>
To: Rick Macklem <rmacklem@uoguelph.ca>
Subject: Re: Terrible NFS performance under 9.2-RELEASE?
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<<On Sat, 25 Jan 2014 21:36:26 -0500 (EST), Rick Macklem <rmacklem@uoguelph.ca> said:

> Have you tried increasing readahead by any chance? I think the default
> is 1, which means the client will make 2 read requests and then wait for
> those replies before doing any more reads. Since you have fast links,
> maybe the 2 * 64K reads isn't enough to keep the pipe filled? (This
> depends on latency, which you didn't mention.)

-o readahead=4 nearly doubles the speed, to a bit over 5 Gbit/s.

Oddly, when I unmount the filesystem, the test client sometimes
freezes for 15-30 seconds.  Since I'm not on the console I can't tell
what it's doing when this happens.

-GAWollman