Re: Clearing the I/O caches? (for benchmark tests)

Stephen C. Tweedie (sct@redhat.com)
Thu, 15 Jul 1999 12:56:20 +0100 (BST)


Hi,

On 14 Jul 1999 16:42:47 -0700, tmk@cse.ucsc.edu (Tom M. Kroeger) said:

> In any case the memory exhausting approach still cleared far more
> space than sys_sync & invalidate_buffers etc... (are these buffers
> taken from ext2 when memory becomes very low?) Any idea as to why?

Of course it will. Invalidating buffers etc. won't do anything about
the page cache. A memory flush will also flush out the page cache very
effectvely.

> You said ext2 keeps "recently-accessed bitmap buffers pinned", can
> I just wait 30 second ( or however long) and then re-run the test?

No. The last 8 inode and bitmap buffers accessed are pinned forever (or
until a different buffer evicts one from the cache).

--Stephen

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