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On Wednesday 20 July 2011 13:30:05 Grant did opine thusly: |
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> I ran into an out of memory problem. The first mention of it in the |
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> kernel log is "mysqld invoked oom-killer". I haven't run into this |
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> before. I do have a swap partition but I don't activate it based |
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> on something I read previously that I later found out was wrong so |
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> I suppose I should activate it. Is fstab the way to do that? I |
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> have a commented line in there for swap. |
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> |
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> Can anyone tell how much swap this is: |
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> |
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> /dev/sda2 80325 1140614 530145 82 Linux swap / |
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> Solaris |
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> |
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> If it's something like 512MB, that may not have prevented me from |
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> running out of memory since I have 4GB RAM. Is there any way to |
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> find out if there was a memory leak or other problem that should be |
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> investigated? |
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To activate swap, put a line in fstab like so: |
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/dev/sda2 none swap sw 0 0 |
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However, you do not want to use it. it is not the life-saver some |
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howto authors on the internet claim it to be. |
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When a linux machine hits swap, it does so very aggressively, there is |
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nothing nice about it at all. The entire machine slows to a |
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painstaking crawl for easily a minute at a time while the kernel |
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writes pages out to disk, and disk is thousands of times slower than |
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RAM. |
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It gets so bad that you can't even run a shell properly to try and see |
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what's going on and kill the actual memory hog. |
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My personal rule of thumb: if you hit swap, the bad thing has already |
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gone very very south, usually to the point where you can't do much |
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about it and it's already too late. Besides, that bastard deomon spawn |
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of satan called the oom-killer is likely about to kick in and REALLY |
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make your day. Anyone else notice how oom-killer seems to be hard |
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coded to zap the most inconvenient process of all?..... |
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What you need to be doing is monitor your memory usage during normal |
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conditions and deal with issues before they become problems. |
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-- |
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alan dot mckinnon at gmail dot com |
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