[Lustre-discuss] Fwd: Lustre and Large Pages

[John Hammond]

Hi Andreas,

On 08/19/2010 06:07 PM, Andreas Dilger wrote:
> On 2010-08-19, at 16:44, Kevin Van Maren wrote:
>> Easy way to reduce the client memory used by "Lustre" is to have
>> an Epilogue script run by SGE (or whatever scheduler/resource
>> manager) that does something like this on every node: # sync ;
>> sleep 1 ; sync # echo 3>  /proc/sys/vm/drop_caches
>
> Actually, my understanding is that /proc/sys/vm/drop_caches is NOT
> safe for production usage in all cases (i.e. there are bugs in some
> kernels, and it isn't actually meant for regular use from what I've
> read).

That's good to know.  But, there are two parts to drop_caches, depending 
on what you write---do you know if the unsafety comes from the part that 
calls the 'slab' shrinkers or the part that calls 
invalidate_inode_pages()?  I suppose it's the latter.  Do you have a 
pointer to a more specific description?  I'm curious about which kernels 
are affected.  I looked but didn't turn up much.

Thanks,

-John

-- 
John L. Hammond, Ph.D.
ICES, The University of Texas at Austin
jhammond at ices.utexas.edu
(512) 471-9304