linux-kernel - Re: [RFC][Resend] Make NFS-Client readahead tunable

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Message-ID: <614333.44648.qm@web32604.mail.mud.yahoo.com>
Date:	Sun, 21 Sep 2008 05:53:32 -0700 (PDT)
From:	Martin Knoblauch <knobi@...bisoft.de>
To:	Peter Staubach <staubach@...hat.com>,
	Chuck Lever <chucklever@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Banks <gnb@...bourne.sgi.com>,
	linux-nfs list <linux-nfs@...r.kernel.org>,
	linux-kernel@...r.kernel.org,
	Peter zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC][Resend] Make NFS-Client readahead tunable



> >
> > I agree that a mount option would allow more fine-grained control over
> > readahead.  A system wide parameter controlling readahead has always
> > been a weakness.  Readahead, as implemented in the VFS, has a
> > *per-file descriptor* context, however, which operates automatically
> > (and can be tuned at run-time by an application with [mf]advise(2).
> >
> > As a future feature, this might work in better combination with the
> > per-mount bdi changes proposed by Peter to provide maximal flexibility
> > without exposing yet another confusing knob that could help some
> > workloads but hurt others.
> 
> And perhaps add some dynamic tuning capabilities to the NFS client
> code to just make it do "the right thing".  This would be better
> than any tunables and would help to serve in other situations, such
> as high bandwidth/latency networks, overloaded servers who don't
> need more read-ahead READ requests piled on, etc...
> 

 this goes over my capabilities, but would certainly help the situation. But then I would hate to see Sun/Linux going off the hook, because Linux just played nice :-)

Cheers
Martin

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