Hi, Kamil, I suppose you'd rather not see such an issue than pursue the ugly work-around to kill off processes. In such situations, the first looks should be for the GPFS log (on the client, on the cluster manager, and maybe on the file system manager) and for the current waiters (that is the list of currently waiting threads) on the hanging client.
-> /var/adm/ras/mmfs.log.latest mmdiag --waiters That might give you a first idea what is taking long and which components are involved. Also, mmdiag --iohist shows you the last IOs and some stats (service time, size) for them. Either that clue is already sufficient, or you go on (if you see DIO somewhere, direct IO is used which might slow down things, for example). GPFS has a nice tracing which you can configure or just run the default trace. Running a dedicated (low-level) io trace can be achieved by mmtracectl --start --trace=io --tracedev-write-mode=overwrite -N <your_critical_node> then, when the issue is seen, stop the trace by mmtracectl --stop -N <your_critical_node> Do not wait to stop the trace once you've seen the issue, the trace file cyclically overwrites its output. If the issue lasts some time you could also start the trace while you see it, run the trace for say 20 secs and stop again. On stopping the trace, the output gets converted into an ASCII trace file named trcrpt.*(usually in /tmp/mmfs, check the command output). There you should see lines with FIO which carry the inode of the related file after the "tag" keyword. example: 0.000745100 25123 TRACE_IO: FIO: read data tag 248415 43466 ioVecSize 8 1st buf 0x299E89BC000 disk 8D0 da 154:2083875440 nSectors 128 err 0 finishTime 1563473283.135212150 -> inode is 248415 there is a utility , tsfindinode, to translate that into the file path. you need to build this first if not yet done: cd /usr/lpp/mmfs/samples/util ; make , then run ./tsfindinode -i <inode_num> <fs_mount_point> For the IO trace analysis there is an older tool : /usr/lpp/mmfs/samples/debugtools/trsum.awk. Then there is some new stuff I've not yet used in /usr/lpp/mmfs/samples/traceanz/ (always check the README) Hope that halps a bit. Mit freundlichen Grüßen / Kind regards Dr. Uwe Falke IT Specialist Hybrid Cloud Infrastructure / Technology Consulting & Implementation Services +49 175 575 2877 Mobile Rathausstr. 7, 09111 Chemnitz, Germany uwefa...@de.ibm.com IBM Services IBM Data Privacy Statement IBM Deutschland Business & Technology Services GmbH Geschäftsführung: Sven Schooss, Stefan Hierl Sitz der Gesellschaft: Ehningen Registergericht: Amtsgericht Stuttgart, HRB 17122 From: "Czauz, Kamil" <kamil.cz...@squarepoint-capital.com> To: "gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org> Date: 11/11/2020 23:36 Subject: [EXTERNAL] [gpfsug-discuss] Poor client performance with high cpu usage of mmfsd process Sent by: gpfsug-discuss-boun...@spectrumscale.org We regularly run into performance issues on our clients where the client seems to hang when accessing any gpfs mount, even something simple like a ls could take a few minutes to complete. This affects every gpfs mount on the client, but other clients are working just fine. Also the mmfsd process at this point is spinning at something like 300-500% cpu. The only way I have found to solve this is by killing processes that may be doing heavy i/o to the gpfs mounts - but this is more of an art than a science. I often end up killing many processes before finding the offending one. My question is really about finding the offending process easier. Is there something similar to iotop or a trace that I can enable that can tell me what files/processes and being heavily used by the mmfsd process on the client? -Kamil Confidentiality Note: This e-mail and any attachments are confidential and may be protected by legal privilege. If you are not the intended recipient, be aware that any disclosure, copying, distribution or use of this e-mail or any attachment is prohibited. If you have received this e-mail in error, please notify us immediately by returning it to the sender and delete this copy from your system. We will use any personal information you give to us in accordance with our Privacy Policy which can be found in the Data Protection section on our corporate website www.squarepoint-capital.com. Please note that e-mails may be monitored for regulatory and compliance purposes. Thank you for your cooperation. _______________________________________________ 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