Re: clustering page-ins

Chuck Lever (cel@monkey.org)
Mon, 19 Jul 1999 17:39:55 -0400 (EDT)


On Mon, 19 Jul 1999, Benjamin LaHaise wrote:
> Here's where I'm not quite following you -- do you agree that read-ahead
> is a good thing? The statement that overall efficiency of the system
> drops as readahead is increased is, in my opinion, false.

reading lots of data you don't use is not good for performance. also,
reading ahead in some instances, even if the data is useful, evicts some
cached data that may have to be read again. i'm just suggesting that
reading ahead in a narrow and greedy way can be very destructive to
overall system performance.

> However, if you're arguing that blindly pulling in a cluster's worth of
> data without any real heuristics is somewhat detrimental to peformance, I
> agree.

yeah, that's basically the point :)

> Personally I'd like to see the same intelligence used on both
> files and mmaps (even metadata in some cases) as their access patterns are
> often interchangable (think samba, grep, ...).

yes, that might even be useful if we're careful about it, and i think i
can give that a try.

- Chuck Lever

--
corporate:	<chuckl@netscape.com>
personal:	<chucklever@netscape.net> or <cel@monkey.org>

The Linux Scalability project: http://www.citi.umich.edu/projects/linux-scalability/

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