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<div class="moz-cite-prefix">From the top's sent before, it looks
like the administrators might have configured the system with no
swap:<br>
<br>
r1i1n2<br>
<br>
Swap: 0M total, 0M used, 0M free, 10563M
cached<br>
<br>
r1i1n3<br>
<br>
Swap: 0M total, 0M used, 0M free, 23089M
cached<br>
<br>
Keep in mind that having swap might mean the difference between
hurt performance and a hard crash under low memory [
<a class="moz-txt-link-freetext" href="http://unix.stackexchange.com/questions/190398/do-i-need-swap-space-if-i-have-more-than-enough-amount-of-ram">http://unix.stackexchange.com/questions/190398/do-i-need-swap-space-if-i-have-more-than-enough-amount-of-ram</a>
].<br>
<br>
On 9/29/2015 5:57 AM, Laurence Marks wrote:<br>
</div>
<blockquote
cite="mid:CANkSMZBkycQawCXUkqVxcGY4VvTV6ePc9WW_LfAG+ZPp=rOp0Q@mail.gmail.com"
type="cite">
<p dir="ltr">If it happens again, one thing to ask them to check
is swap usage and how much memory is cached. On some of my nodes
I have noticed that they do not always release cached memory,
and can start swapping. If this happens the job will get very
slow. The commands to use to clear the cache can be found at <br>
<a moz-do-not-send="true"
href="http://www.tecmint.com/clear-ram-memory-cache-buffer-and-swap-space-on-linux/">http://www.tecmint.com/clear-ram-memory-cache-buffer-and-swap-space-on-linux/</a>
or similar. (Needs root access.) Top can also show memory use.</p>
<p dir="ltr">While there should be no need to do this, I have
noticed that I need to do it every 3hrs on 4 nodes - the other
20 don't need it. It is an issue mainly for big calculations.</p>
<p dir="ltr">Alternatively it was something else, a zombie, big
log files or other things. Rebooting gets rid of a lot of system
caches and helps -- even on my Android tablet every week or two.
It's murky waters.</p>
<p dir="ltr">---<br>
Professor Laurence Marks<br>
Department of Materials Science and Engineering<br>
Northwestern University<br>
<a moz-do-not-send="true"
href="http://www.numis.northwestern.edu">http://www.numis.northwestern.edu</a><br>
Corrosion in 4D<a moz-do-not-send="true"
href="http://MURI4D.numis.northwestern.edu">
http://MURI4D.numis.northwestern.edu</a><br>
Co-Editor, Acta Cryst A<br>
"Research is to see what everybody else has seen, and to think
what nobody else has thought"<br>
Albert Szent-Gyorgi</p>
</blockquote>
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