2008-09-21 12:53:33

by Martin Knoblauch

[permalink] [raw]
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 :-)