[lustre-discuss] lester on mds with low memory

Mohr Jr, Richard Frank (Rick Mohr) rmohr at utk.edu
Fri Mar 27 08:52:29 PDT 2015

> On Mar 27, 2015, at 4:38 AM, Alexander Oltu <Alexander.Oltu at uib.no> wrote:
> yes, right before starting Lester. I tried sending 1 and sending 3 to /proc/sys/vm/drop_caches, maximum I can get is 1.5 GB.
> I don’t know where the buffer memory is being used. Running “sync” didn’t change anything. I was thinking maybe this is something Lustre related.

I wonder if it is possible that you are hitting LU-5726.  You might want to check the “Inactive(file)” line in /proc/meminfo to see if that accounts for most of the buffer usage.  When I was hitting this bug, dropping caches would have no effect and I could not reclaim memory on my MDS server.  After I applied the patch, I could consistently run “echo 3 > /proc/sys/vm/drop_caches” and reclaim almost all the memory on the MDS.

Rick Mohr
Senior HPC System Administrator
National Institute for Computational Sciences

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