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Grant wrote: |
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>>Swap enables the system to have more memory pages for the running processes. If |
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>>the OS doesn't have enough memory for a process, it'll let the process know, or |
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>>simply kill it. |
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>> |
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>>If you don't want swap to be used, disable it. Remember that the system also |
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>>uses physical ram for caching disk, not only for user processes. |
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>> |
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>>If you don't use swap, your 'inactive' processes won't go into swap. Maybe the |
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>>OS prefers having more disk into cache than a process in physical ram. (there |
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>>must be rules in Linux for that). Then, when your usually-inactive process is |
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>>awakened, the OS must move its pages from disk to RAM, shown as a slow answer |
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>>from that process. |
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>> |
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>>Reaching your memory limit without swap, is the same as reaching the memory |
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>>limit with swap (physical + disk). Someone who maintains a system, must select a |
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>>reasonable amount of 'swap' according to the expected behaviour of that system. |
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>>What do you want, be able of running more processes than your physical RAM |
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>>enables -use swap- against some slowness, or keep on your physical RAM limit, |
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>>keeping a normal system speed for all processes? |
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>> |
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>>conclusion: you're absolutely free for disabling your swap. System doesn't |
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>>require swap for "some reason", as you said. |
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>> |
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>> |
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> |
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>OK, I'm getting a better grip on memory and swap thanks to you guys. |
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>Let me ask this another way though. |
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> |
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>I doesn't seem like disabling swap is such a good idea, especially on |
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>a commercial server and especially when I'm going to be running a |
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>second instance of the OS inside VMware. What if my site gets a bunch |
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>of traffic for whatever reason all of a sudden? Maybe I'm compiling |
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>my kernel at the same time, and running all kinds of tests in the |
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>VMware'd OS. It seems like the swap needs to be there for times when |
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>the system is really strained and the memory fills up with active |
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>stuff. I remember when I was just starting with Gentoo I forgot to |
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>enable the swap and kept getting an out of memory error during the |
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>bootstrap. |
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> |
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>Maybe a better way to phrase my question is: Is it possible to set my |
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>server up so it will use swap when it needs it and then free it back |
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>up when it doesn't need it anymore? What makes me think that is |
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>necessary is the fact that I see a very snappy response when browsing |
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>my site after a fresh reboot. After it's been up for awhile, the swap |
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>starts to fill and it slows down. Rebooting clears out the swap and |
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>the snaps return. |
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> |
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>All I'm trying to do here is keep my site nice and fast. |
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> |
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> |
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Hey Grant, this may not help, but I'm reading posts about disk cache |
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going into physical memory, and I thought of something. Since you get |
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better performance when you reboot, try this command as root: |
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#sync |
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See if that helps. That basically flushes the cache and sends it to |
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disk where it would eventually go anyway. If so, then you know what's |
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hogging all your memory. |
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James |
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-- |
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My blog: http://www.crazydrclaw.com/ |
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My homepage: http://james.colannino.org/ |
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"Black holes are where God divided by zero." --Steven Wright |
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-- |
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