Difference between revisions of "Swap"
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| − | + | Swap a secondary storage for [[memory]] that is swapped or paged out, usually residing on your hard disk. | |
| + | |||
| + | It is also used for saving the [[kernel]] [[core]]file when the system [[panic]]s. Some systems compress their corefile to swap and others don't (such as [[BSD]]), this is why it's a good idea to have 1.5 to 2 times as much swap as physical memory in a machine (as a rule of thumb), so that you can get a good corefile. | ||
| + | |||
| + | Don't forget to ensure there is always enough room in your swap if your RAM is being used to its maximum capacity: | ||
| + | # swapinfo | ||
| + | Device 1K-blocks Used Avail Capacity | ||
| + | /dev/ad0s1b 105288 68596 36692 65% | ||
| + | |||
| + | otherwise you'll start getting errors to syslog, running applications will be killed, and it will create a general | ||
| + | mess of things: | ||
| + | |||
| + | Oct 27 09:51:38 mail swap_pager_getswapspace(9): failed | ||
| + | Oct 27 09:51:38 mail swap_pager_getswapspace(5): failed | ||
| + | Oct 27 09:51:38 mail swap_pager_getswapspace(16): failed | ||
| + | Oct 27 09:51:40 mail pid 95400 (perl5.8.7), uid 125, was killed: out of swap space | ||
| + | |||
| + | If you are running out of swapspace frequently, or just want to increase the capacity, you can [http://www.freebsd.org/handbook/adding-swap-space.html add a swapfile ]very easily on [[FreeBSD]]. | ||
Revision as of 12:42, 27 October 2005
Swap a secondary storage for memory that is swapped or paged out, usually residing on your hard disk.
It is also used for saving the kernel corefile when the system panics. Some systems compress their corefile to swap and others don't (such as BSD), this is why it's a good idea to have 1.5 to 2 times as much swap as physical memory in a machine (as a rule of thumb), so that you can get a good corefile.
Don't forget to ensure there is always enough room in your swap if your RAM is being used to its maximum capacity:
# swapinfo Device 1K-blocks Used Avail Capacity /dev/ad0s1b 105288 68596 36692 65%
otherwise you'll start getting errors to syslog, running applications will be killed, and it will create a general mess of things:
Oct 27 09:51:38 mail swap_pager_getswapspace(9): failed Oct 27 09:51:38 mail swap_pager_getswapspace(5): failed Oct 27 09:51:38 mail swap_pager_getswapspace(16): failed Oct 27 09:51:40 mail pid 95400 (perl5.8.7), uid 125, was killed: out of swap space
If you are running out of swapspace frequently, or just want to increase the capacity, you can add a swapfile very easily on FreeBSD.
