RE: [2.4.17/18pre] VM and swap - it's really unusable

[M. Edward Borasky]

> My main "problem" with 2.4 as well. Using free memory for Cache/Buffers
> is great, but only as long as the memory is not needed for running
> tasks. As soon as a task is requesting more memory, it should be first
> taken from Cache/Buffer (they are caches, aren't they :-). Only if this
> has been used up (to a tunable minimum, see below), swapping and finally
> OOM killing should happen.
>
> To prevent completely trashing IO performance, there should be tunable
> parameters for minimum and maximum Cache/Buffer usage (lets say in
> percent of total memory). Maybe those tunables are even there today and
> I am just to stupid to find them :-))

Yes!! I second that motion!! On top of that, we need buffer/page cache hit
rate statistics!! Once your read hit rate gets up into the high 90
percentages, more buffer/page cache memory is wasted.

If Linux is to succeed in enterprise-level usage, we *must* have tools to
measure, manage and tune performance -- in short, to do capacity planning
like we do on any other system. And the kernel variables that affect
performance *must* be under control of the system administrator and
ultimately the machine's *customers*, *not* a bunch of kernel geeks! That
means keeping them in variables accessible by a system administrator, *not*
#defines in code that must be entirely recompiled when you want to tweak a
parameter.

If you build it, they will come :). If you *refuse* to build it, they will
use something else -- it's as simple as that.
--
M. Edward Borasky

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http://www.borasky-research.net