[gpfsug-discuss] Performance problems + (MultiThreadWorkInstanceCond), reason 'waiting for helper threads'

Thu Apr 18 18:41:45 BST 2019

Hi,

thanks a lot. About the requested information:

* Waiters were captured with the command 'mmdiag --waiters', and it was performed on one of the IO (NSD) nodes.
* Connection between storage and client clusters is with Infiniband EDR. For the GPFS client cluster we have 3 chassis, each one has 24 blades with unmanaged EDR switch (24 for the blades, 12 external), and currently 10 EDR external ports are connected for external connectivity. On the other hand, the GPFS storage cluster has 2 IO nodes (as commented in the previous e-mail, DSS G240). Each IO node has connected 4 x EDR ports. Regarding the Infiniband connectivty, my network contains 2 top EDR managed switches configured with up/down routing, connecting the unmanaged switches from the chassis and the 2 managed Infiniband switches for the storage (for redundancy).

Whenever needed I can go through PMR if this would easy the debug, no problem for me. I was wondering about the meaning "waiting for helper threads" and what could be the reason for that

Thanks a lot for your help and best regards,
Marc
_________________________________________
Paul Scherrer Institut
High Performance Computing
Marc Caubet Serrabou
Building/Room: WHGA/019A
Forschungsstrasse, 111
5232 Villigen PSI
Switzerland

Telephone: +41 56 310 46 67
E-Mail: marc.caubet at psi.ch
________________________________
From: gpfsug-discuss-bounces at spectrumscale.org [gpfsug-discuss-bounces at spectrumscale.org] on behalf of IBM Spectrum Scale [scale at us.ibm.com]
Sent: Thursday, April 18, 2019 5:54 PM
To: gpfsug main discussion list
Cc: gpfsug-discuss-bounces at spectrumscale.org
Subject: Re: [gpfsug-discuss] Performance problems + (MultiThreadWorkInstanceCond), reason 'waiting for helper threads'

We can try to provide some guidance on what you are seeing but generally to do true analysis of performance issues customers should contact IBM lab based services (LBS).  We need some additional information to understand what is happening.

  *   On which node did you collect the waiters and what command did you run to capture the data?
  *   What is the network connection between the remote cluster and the storage cluster?

Regards, The Spectrum Scale (GPFS) team

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From:        "Caubet Serrabou Marc (PSI)" <marc.caubet at psi.ch>
To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:        04/18/2019 11:41 AM
Subject:        [gpfsug-discuss] Performance problems + (MultiThreadWorkInstanceCond), reason 'waiting for helper threads'
Sent by:        gpfsug-discuss-bounces at spectrumscale.org
________________________________

Hi all,

I would like to have some hints about the following problem:

Waiting 26.6431 sec since 17:18:32, ignored, thread 38298 NSPDDiscoveryRunQueueThread: on ThCond 0x7FC98EB6A2B8 (MultiThreadWorkInstanceCond), reason 'waiting for helper threads'
Waiting 2.7969 sec since 17:18:55, monitored, thread 39736 NSDThread: for I/O completion
Waiting 2.8024 sec since 17:18:55, monitored, thread 39580 NSDThread: for I/O completion
Waiting 3.0435 sec since 17:18:55, monitored, thread 39448 NSDThread: for I/O completion

I am testing a new GPFS cluster (GPFS cluster client with computing nodes remotely mounting the Storage GPFS Cluster) and I am running 65 gpfsperf commands (1 command per client in parallell) as follows:

/usr/lpp/mmfs/samples/perf/gpfsperf create seq /gpfs/home/caubet_m/gpfsperf/$(hostname).txt -fsync -n 24g -r 16m -th 8

I am unable to reach more than 6.5GBps (Lenovo DSS G240 GPFS 5.0.2-1, on a testing a 'home' filesystem with 1MB blocksize and subblocks of 8KB). After several seconds I see many waiters for I/O completion (up to 5 seconds)
and also the 'waiting for helper threads' message shown above. Can somebody explain me the meaning for this message? How could I improve that?

Current config in the storage cluster is:

[root at merlindssio02 ~]# mmlsconfig
Configuration data for cluster merlin.psi.ch:
---------------------------------------------
clusterName merlin.psi.ch
clusterId 1511090979434548295
autoload no
dmapiFileHandleSize 32
minReleaseLevel 5.0.2.0
ccrEnabled yes
nsdRAIDFirmwareDirectory /opt/lenovo/dss/firmware
cipherList AUTHONLY
maxblocksize 16m
[merlindssmgt01]
ignorePrefetchLUNCount yes
[common]
pagepool 4096M
[merlindssio01,merlindssio02]
pagepool 270089M
[merlindssmgt01,dssg]
pagepool 57684M
maxBufferDescs 2m
numaMemoryInterleave yes
[common]
prefetchPct 50
[merlindssmgt01,dssg]
prefetchPct 20
nsdRAIDTracks 128k
nsdMaxWorkerThreads 3k
nsdMinWorkerThreads 3k
nsdRAIDSmallThreadRatio 2
nsdRAIDThreadsPerQueue 16
nsdClientCksumTypeLocal ck64
nsdClientCksumTypeRemote ck64
nsdRAIDFlusherFWLogHighWatermarkMB 1000
nsdRAIDBlockDeviceMaxSectorsKB 0
nsdRAIDBlockDeviceNrRequests 0
nsdRAIDBlockDeviceQueueDepth 0
nsdRAIDBlockDeviceScheduler off
nsdRAIDMaxPdiskQueueDepth 128
nsdMultiQueue 512
verbsRdma enable
verbsPorts mlx5_0/1 mlx5_1/1
verbsRdmaSend yes
scatterBufferSize 256K
maxFilesToCache 128k
maxMBpS 40000
workerThreads 1024
nspdQueues 64
[common]
subnets 192.168.196.0/merlin-hpc.psi.ch;merlin.psi.ch
adminMode central

File systems in cluster merlin.psi.ch:
--------------------------------------
/dev/home
/dev/t16M128K
/dev/t16M16K
/dev/t1M8K
/dev/t4M16K
/dev/t4M32K
/dev/test

And for the computing cluster:

[root at merlin-c-001 ~]# mmlsconfig
Configuration data for cluster merlin-hpc.psi.ch:
-------------------------------------------------
clusterName merlin-hpc.psi.ch
clusterId 14097036579263601931
autoload yes
dmapiFileHandleSize 32
minReleaseLevel 5.0.2.0
ccrEnabled yes
cipherList AUTHONLY
maxblocksize 16M
numaMemoryInterleave yes
maxFilesToCache 128k
maxMBpS 20000
workerThreads 1024
verbsRdma enable
verbsPorts mlx5_0/1
verbsRdmaSend yes
scatterBufferSize 256K
ignorePrefetchLUNCount yes
nsdClientCksumTypeLocal ck64
nsdClientCksumTypeRemote ck64
pagepool 32G
subnets 192.168.196.0/merlin-hpc.psi.ch;merlin.psi.ch
adminMode central

File systems in cluster merlin-hpc.psi.ch:
------------------------------------------
(none)

Thanks a lot and best regards,
Marc
_________________________________________
Paul Scherrer Institut
High Performance Computing
Marc Caubet Serrabou
Building/Room: WHGA/019A
Forschungsstrasse, 111
5232 Villigen PSI
Switzerland

Telephone: +41 56 310 46 67
E-Mail: marc.caubet at psi.ch_______________________________________________
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