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<div>Thanks to all for clarification.</div>
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<div id="divRpF69233" style="direction: ltr;"><font size="2" face="Tahoma" color="#000000"><b>From:</b> gpfsug-discuss-bounces@spectrumscale.org [gpfsug-discuss-bounces@spectrumscale.org] on behalf of Tomer Perry [TOMP@il.ibm.com]<br>
<b>Sent:</b> Wednesday, March 06, 2019 2:14 PM<br>
<b>To:</b> gpfsug main discussion list<br>
<b>Subject:</b> Re: [gpfsug-discuss] Memory accounting for processes writing to GPFS<br>
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<div><font size="2" face="sans-serif">It might be the case that </font><font size="2" face="Tahoma">AsynchronousFileChannel</font><font size="2" face="sans-serif">is actually doing mmap access to the files. Thus, the memory management will be completely different
with GPFS in compare to local fs.</font><br>
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Regards,<br>
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Tomer Perry<br>
Scalable I/O Development (Spectrum Scale)<br>
email: tomp@il.ibm.com<br>
1 Azrieli Center, Tel Aviv 67021, Israel<br>
Global Tel: +1 720 3422758<br>
Israel Tel: +972 3 9188625<br>
Mobile: +972 52 2554625<br>
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<font size="1" face="sans-serif" color="#5f5f5f">From: </font><font size="1" face="sans-serif">Jim Doherty <jjdoherty@yahoo.com></font><br>
<font size="1" face="sans-serif" color="#5f5f5f">To: </font><font size="1" face="sans-serif">gpfsug main discussion list <gpfsug-discuss@spectrumscale.org></font><br>
<font size="1" face="sans-serif" color="#5f5f5f">Date: </font><font size="1" face="sans-serif">06/03/2019 06:59</font><br>
<font size="1" face="sans-serif" color="#5f5f5f">Subject: </font><font size="1" face="sans-serif">Re: [gpfsug-discuss] Memory accounting for processes writing to GPFS</font><br>
<font size="1" face="sans-serif" color="#5f5f5f">Sent by: </font><font size="1" face="sans-serif">gpfsug-discuss-bounces@spectrumscale.org</font><br>
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<font size="2" face="Helvetica">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.
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<font size="2" face="Helvetica">I look to /proc/$pid/status to find the memory used by a proc RSS + Swap + kernel page tables. </font><br>
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<font size="2" face="Helvetica">Jim</font><br>
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<font size="2" face="Helvetica Neue" color="#2f2f2f">On Wednesday, March 6, 2019, 4:25:48 AM EST, Dorigo Alvise (PSI) <alvise.dorigo@psi.ch> wrote:
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<font size="2" face="Tahoma">Hello to everyone,</font><br>
<font size="2" face="Tahoma">Here a PSI we're observing something that in principle seems strange (at least to me).</font><br>
<font size="2" face="Tahoma">We run a Java application writing into disk by mean of a standard AsynchronousFileChannel, whose I do not the details.</font><br>
<font size="2" face="Tahoma">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).</font><br>
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<font size="2" face="Tahoma">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).</font><br>
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<font size="2" face="Tahoma">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 ?</font><br>
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<font size="2" face="Tahoma">thanks in advance,</font><br>
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<font size="2" face="Tahoma"> Alvise</font><br>
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