Re: clearing filesystem cache for I/O benchmarks

[Nathan Scott]

On Mon, Jul 26, 2004 at 11:40:05PM -0700, Andrew Morton wrote:
> ...
> However...  If you write any amount of data to a file with O_DIRECT, that
> will, as a side-effect, remove _all_ of that file's pagecache.  In 2.4 as
> well as 2.6.  So you could scrub the pagecache by reading the first 4k then
> writing it back with O_DIRECT.
> 
> However O_DIRECT is supported on very few filesystems in 2.4.  ext2 and
> reiserfs have it.
> 
> XFS in 2.4 has O_DIRECT, I think, but I don't know if the invalidation
> side-effect works on XFS.

Yep, it does.

cheers.

-- 
Nathan
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