Re: [PATCH 0/4] linux-2.6-block: deactivating pagecache for benchmarks

[Jeff Garzik]

On Thu, Dec 01, 2005 at 05:25:20PM -0800, Andrew Morton wrote:
> Dirk Henning Gerdes <mail@xxxxxxxxxxxxxx> wrote:
> >
> >  For doing benchmarks on the I/O-Schedulers, I thought it would be very
> >  useful to disable the pagecache.
> 
> That's an FAQ.   Something like this?
> 
> 
> From: Andrew Morton <akpm@xxxxxxxx>
> 
> Add /proc/sys/vm/drop-pagecache.  When written to, this will cause the kernel
> to discard as much pagecache and reclaimable slab objects as it can.
> 
> It won't drop dirty data, so the user should run `sync' first.
> 
> Caveats:
> 
> a) Holds inode_lock for exorbitant amounts of time.
> 
> b) Needs to be taught about NUMA nodes: propagate these all the way through
>    so the discarding can be controlled on a per-node basis.
> 
> c) The pagecache shrinking and slab shrinking should probably have separate
>    controls.
> 
> 
> Signed-off-by: Andrew Morton <akpm@xxxxxxxx>

ACK, I've wanted something like this for a while.

I really think it should be a config option, though, to discourage
people from building with it :)

	Jeff



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