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Re: OT (slightly) swap limits

Ron Johnson wrote:
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On 04/26/08 18:13, Bob Proulx wrote:
I learned about this because I didn't know it when I set up a computer
server pool to be used for some large memory consuming simulations.
They all had 16G of RAM with 64-bit process space.  I knew that if
they started swapping that they would run to slowly for us and the
plan was to avoid swapping.  If they don't swap they don't need swap
space and so I didn't configure any on them.  I came from a Unix
background and didn't expect this different behavior when running on
Linux.  We started to see processes randomly stop running.  Nothing
was ever logged from the log files for those processes.  Large memory
applications never recorded being out of memory.  They just stopped
running.  A number of folks started cursing Linux for being unreliable
and at that moment for us it was very unreliable!  It was from that
experience I learned about the Linux memory overcommit and oom killer
behavior.  And with that knowledge I knew that I needed to rebuild the
computer server pool with overcommit off and enough VM.


This was a very interesting post.  Just now I modified sysconf and
boosted swap up to 2x RAM.
I had skipped Bob's post and had to go back in the archives to read it. I'm glad that I did. Could this be the reason that Firefox sometimes just disappears? No warning. No noticeable problems, just, suddenly, no Firefox. I can't, offhand, remember it happening with other programs, but it might have, so it might just be a Firefox thing, but Bob's post got me wondering. Can I avoid this vanishing trick of Firefox by increasing swap and turning off overcommit? If so, it would be a good thing.

Marc Shapiro

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