Oh, and I think you're absolutely right about the rdma interaction. If I
stop the infiniband service on a node and try the same exercise again, I
can jump between 100G and 1G several times and the free'd memory is
actually released.
-Aaron
On 2/25/18 11:54 AM, Aaron Knister wrote:
Hi Stijn,
Thanks for sharing your experiences-- I'm glad I'm not the only one
whose had the idea (and come up empty handed).
About the pagpool and numa awareness, I'd remembered seeing something
about that somewhere and I did some googling and found there's a
parameter called numaMemoryInterleave that "starts mmfsd with numactl
--interleave=all". Do you think that provides the kind of numa awareness
you're looking for?
-Aaron
On 2/23/18 9:44 AM, Stijn De Weirdt wrote:
hi all,
we had the same idea long ago, afaik the issue we had was due to the
pinned memory the pagepool uses when RDMA is enabled.
at some point we restarted gpfs on the compute nodes for each job,
similar to the way we do swapoff/swapon; but in certain scenarios gpfs
really did not like it; so we gave up on it.
the other issue that needs to be resolved is that the pagepool needs to
be numa aware, so the pagepool is nicely allocated across all numa
domains, instead of using the first ones available. otherwise compute
jobs might start that only do non-local doamin memeory access.
stijn
On 02/23/2018 03:35 PM, IBM Spectrum Scale wrote:
AFAIK you can increase the pagepool size dynamically but you cannot
shrink
it dynamically. To shrink it you must restart the GPFS daemon. Also,
could you please provide the actual pmap commands you executed?
Regards, The Spectrum Scale (GPFS) team
------------------------------------------------------------------------------------------------------------------
If you feel that your question can benefit other users of Spectrum
Scale
(GPFS), then please post it to the public IBM developerWroks Forum at
https://www.ibm.com/developerworks/community/forums/html/forum?id=11111111-0000-0000-0000-000000000479
.
If your query concerns a potential software error in Spectrum Scale
(GPFS)
and you have an IBM software maintenance contract please contact
1-800-237-5511 in the United States or your local IBM Service Center in
other countries.
The forum is informally monitored as time permits and should not be used
for priority messages to the Spectrum Scale (GPFS) team.
From: Aaron Knister <aaron.s.knis...@nasa.gov>
To: <gpfsug-discuss@spectrumscale.org>
Date: 02/22/2018 10:30 PM
Subject: Re: [gpfsug-discuss] pagepool shrink doesn't release all
memory
Sent by: gpfsug-discuss-boun...@spectrumscale.org
This is also interesting (although I don't know what it really means).
Looking at pmap run against mmfsd I can see what happens after each
step:
# baseline
00007fffe4639000 59164K 0K 0K 0K 0K ---p [anon]
00007fffd837e000 61960K 0K 0K 0K 0K ---p [anon]
0000020000000000 1048576K 1048576K 1048576K 1048576K 0K rwxp [anon]
Total: 1613580K 1191020K 1189650K 1171836K 0K
# tschpool 64G
00007fffe4639000 59164K 0K 0K 0K 0K ---p [anon]
00007fffd837e000 61960K 0K 0K 0K 0K ---p [anon]
0000020000000000 67108864K 67108864K 67108864K 67108864K 0K rwxp
[anon]
Total: 67706636K 67284108K 67282625K 67264920K 0K
# tschpool 1G
00007fffe4639000 59164K 0K 0K 0K 0K ---p [anon]
00007fffd837e000 61960K 0K 0K 0K 0K ---p [anon]
0000020001400000 139264K 139264K 139264K 139264K 0K rwxp [anon]
0000020fc9400000 897024K 897024K 897024K 897024K 0K rwxp [anon]
0000020009c00000 66052096K 0K 0K 0K 0K rwxp [anon]
Total: 67706636K 1223820K 1222451K 1204632K 0K
Even though mmfsd has that 64G chunk allocated there's none of it
*used*. I wonder why Linux seems to be accounting it as allocated.
-Aaron
On 2/22/18 10:17 PM, Aaron Knister wrote:
I've been exploring the idea for a while of writing a SLURM SPANK
plugin
to allow users to dynamically change the pagepool size on a node. Every
now and then we have some users who would benefit significantly from a
much larger pagepool on compute nodes but by default keep it on the
smaller side to make as much physmem available as possible to batch
work.
In testing, though, it seems as though reducing the pagepool doesn't
quite release all of the memory. I don't really understand it because
I've never before seen memory that was previously resident become
un-resident but still maintain the virtual memory allocation.
Here's what I mean. Let's take a node with 128G and a 1G pagepool.
If I do the following to simulate what might happen as various jobs
tweak the pagepool:
- tschpool 64G
- tschpool 1G
- tschpool 32G
- tschpool 1G
- tschpool 32G
I end up with this:
mmfsd thinks there's 32G resident but 64G virt
# ps -o vsz,rss,comm -p 24397
VSZ RSS COMMAND
67589400 33723236 mmfsd
however, linux thinks there's ~100G used
# free -g
total used free shared buffers
cached
Mem: 125 100 25 0 0
0
-/+ buffers/cache: 98 26
Swap: 7 0 7
I can jump back and forth between 1G and 32G *after* allocating 64G
pagepool and the overall amount of memory in use doesn't balloon but I
can't seem to shed that original 64G.
I don't understand what's going on... :) Any ideas? This is with Scale
4.2.3.6.
-Aaron
_______________________________________________
gpfsug-discuss mailing list
gpfsug-discuss at spectrumscale.org
http://gpfsug.org/mailman/listinfo/gpfsug-discuss
_______________________________________________
gpfsug-discuss mailing list
gpfsug-discuss at spectrumscale.org
http://gpfsug.org/mailman/listinfo/gpfsug-discuss
--
Aaron Knister
NASA Center for Climate Simulation (Code 606.2)
Goddard Space Flight Center
(301) 286-2776
_______________________________________________
gpfsug-discuss mailing list
gpfsug-discuss at spectrumscale.org
http://gpfsug.org/mailman/listinfo/gpfsug-discuss
