Re: how to turn off, or to clear read cache?

[Mike Fedyk]

On Wed, Aug 20, 2003 at 11:46:28PM +0100, Jamie Lokier wrote:
> Denis Vlasenko wrote:
> > On 20 August 2003 14:52, Sergey Spiridonov wrote:
> > > I need to make some performance tests. I need to switch off or to clear 
> > > read cache, so that consequent reading of the same file will take the 
> > > same amount of time.
> > 
> > umount/mount cycle will do it, as well as intentional OOMing the box
> > (from non-root account please;)
> 
> umount/mount is impractical when you're testing performance on a big
> filesystem, which is always being used (e.g. /home).
> 
> I'm fairly sure that -o remount used to have this side effect, in fact
> I used it quite a lot for that purpose, so it should be possible to
> make it work again, or add a -o flushcache option.

Won't that hold a lot of locks, and possibly pause the system until the
flushing is complete?  Hopefully, in 2.6 this doesn't call lock_kernel...
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