mmfsadm dump pgalloc might get you one step further ...
Mit freundlichen Grüßen / Kind regards Dr. Uwe Falke IT Specialist High Performance Computing Services / Integrated Technology Services / Data Center Services ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Rathausstr. 7 09111 Chemnitz Phone: +49 371 6978 2165 Mobile: +49 175 575 2877 E-Mail: [email protected] ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Business & Technology Services GmbH / Geschäftsführung: Thomas Wolter, Sven Schooß Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart, HRB 17122 From: Peter Smith <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 02/05/2018 12:10 Subject: Re: [gpfsug-discuss] Confusing I/O Behavior Sent by: [email protected] "how do I see how much of the pagepool is in use and by what? I've looked at mmfsadm dump and mmdiag --memory and neither has provided me the information I'm looking for (or at least not in a format I understand)" +1. Pointers appreciated! :-) On 10 April 2018 at 17:22, Aaron Knister <[email protected]> wrote: I wonder if this is an artifact of pagepool exhaustion which makes me ask the question-- how do I see how much of the pagepool is in use and by what? I've looked at mmfsadm dump and mmdiag --memory and neither has provided me the information I'm looking for (or at least not in a format I understand). -Aaron On 4/10/18 12:00 PM, Knister, Aaron S. (GSFC-606.2)[COMPUTER SCIENCE CORP] wrote: I hate admitting this but I?ve found something that?s got me stumped. We have a user running an MPI job on the system. Each rank opens up several output files to which it writes ASCII debug information. The net result across several hundred ranks is an absolute smattering of teeny tiny I/o requests to te underlying disks which they don?t appreciate. Performance plummets. The I/o requests are 30 to 80 bytes in size. What I don?t understand is why these write requests aren?t getting batched up into larger write requests to the underlying disks. If I do something like ?df if=/dev/zero of=foo bs=8k? on a node I see that the nasty unaligned 8k io requests are batched up into nice 1M I/o requests before they hit the NSD. As best I can tell the application isn?t doing any fsync?s and isn?t doing direct io to these files. Can anyone explain why seemingly very similar io workloads appear to result in well formed NSD I/O in one case and awful I/o in another? Thanks! -Stumped _______________________________________________ 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 -- Peter Smith · Senior Systems Engineer London · New York · Los Angeles · Chicago · Montréal T +44 (0)20 7208 2600 · M +44 (0)7816 123009 28 Chancery Lane, London WC2A 1LB Twitter · Facebook · framestore.com _______________________________________________ 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
