Thanks to all for clarification. A
________________________________ From: [email protected] [[email protected]] on behalf of Tomer Perry [[email protected]] Sent: Wednesday, March 06, 2019 2:14 PM To: gpfsug main discussion list Subject: Re: [gpfsug-discuss] Memory accounting for processes writing to GPFS It might be the case that AsynchronousFileChannelis actually doing mmap access to the files. Thus, the memory management will be completely different with GPFS in compare to local fs. Regards, Tomer Perry Scalable I/O Development (Spectrum Scale) email: [email protected] 1 Azrieli Center, Tel Aviv 67021, Israel Global Tel: +1 720 3422758 Israel Tel: +972 3 9188625 Mobile: +972 52 2554625 From: Jim Doherty <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 06/03/2019 06:59 Subject: Re: [gpfsug-discuss] Memory accounting for processes writing to GPFS Sent by: [email protected] ________________________________ For any process with a large number of threads the VMM size has become an imaginary number ever since the glibc change to allocate a heap per thread. I look to /proc/$pid/status to find the memory used by a proc RSS + Swap + kernel page tables. Jim On Wednesday, March 6, 2019, 4:25:48 AM EST, Dorigo Alvise (PSI) <[email protected]> wrote: Hello to everyone, Here a PSI we're observing something that in principle seems strange (at least to me). We run a Java application writing into disk by mean of a standard AsynchronousFileChannel, whose I do not the details. There are two instances of this application: one runs on a node writing on a local drive, the other one runs writing on a GPFS mounted filesystem (this node is part of the cluster, no remote-mounting). What we do see is that in the former the application has a lower sum VIRT+RES memory and the OS shows a really big cache usage; in the latter, OS's cache is negligible while VIRT+RES is very (even too) high (with VIRT very high). So I wonder what is the difference... Writing into a GPFS mounted filesystem, as far as I understand, implies "talking" to the local mmfsd daemon which fills up its own pagepool... and then the system will asynchronously handle these pages to be written on real pdisk. But why the Linux kernel accounts so much memory to the process itself ? And why this large amount of memory is much more VIRT than RES ? thanks in advance, Alvise _______________________________________________ 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
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