[Gllug] Memory usage when idle

[Andy Farnsworth]

-----Original Message-----
From: Behalf Of Daniel P. Berrange
Sent: Wednesday, May 05, 2004 12:55 PM
To: Greater London Linux Users Group
Subject: Re: [Gllug] Memory usage when idle

Is this including or excluding the mmemory used by the kernel disk cache
the kernel will tend to use all available memory to cache pages from the
disk to maximise I/O performance[1]

[1] Of course this doesn't always go to plan because maximising
    I/O performance in this way impacts on applications responsiveness
    as they get swapped in/out....

-----End Original Message-----

The Linux kernel uses almost all available memory (it will leave
something like 8-16 Mb free) to cache pages from the disk to maximize
I/O performance, however, it will not do so to an extent that it will
cause swap.  These memory pages are flagged as purgable from memory and
therefore if an application needs more memory than is currently
available, the flagged memory pages will be purged (and the disk cache
thus reduced) to allow the application the memory it needs.  This is a
very intelligent way of fully utilizing the resources available on the
machine without causing unwanted slowdown when more memory is needed.

Andy Farnsworth


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