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swap usage monitor

Written on May 20, 2013

Wrote this little thing to keep an eye on how swap usage grows. I find that when it exceeds physical RAM, things get boggy.

#!/bin/sh
PATH=/usr/local/bin:/bin:/sbin:/usr/bin:/usr/sbin:
LAST=`who -b | cut -c18-50`
RAM=`system_profiler SPHardwareDataType | grep Memory | awk '{ print $2 * 1024 }' `
TOTAL=`du -m /var/vm/* | grep swap | awk '{total = total + $1} END {print total}'`
if [ ${TOTAL} -ge ${RAM} ]; then
logger "swap in use = ${TOTAL}, exceeds installed RAM (${RAM}), last reboot was ${LAST}, recommend reboot"
open /var/log/system.log # this opens the log in the Console application so you can see it/can't ignore it.
fi
exit 0

Though, to be fair, it’s not as bad as when I had some useless never-looked-at Dashboard widgets. That was a performance killer. That discovery was inspired by this.I used to check this by simply using

du -sh /var/vm
6.0G    /var/vm

but that didn’t catch that there was a hibernation/sleepimage file in there.

-rw------T  1 root  wheel   4.0G May 22 01:12 sleepimage
-rw-------  1 root  wheel    64M May 22 04:05 swapfile0
-rw-------  1 root  wheel    64M May 22 04:05 swapfile1
-rw-------  1 root  wheel   128M May 22 04:05 swapfile2
-rw-------  1 root  wheel   256M May 22 04:05 swapfile3
-rw-------  1 root  wheel   512M May 22 04:05 swapfile4
-rw-------  1 root  wheel   1.0G May 22 04:05 swapfile5

That’s why I just add up the swapfiles themselves. The one thing I would add is a more informative display of the time since reboot: getting days (?) since reboot would be more informative. But that requires more jiggery-pokery with date(1) than I care to deal with. I’m sure some clever obfuscated perl could be cooked up but I want this to use only tools I know will be available.

Update: this just went off (opened up the Console app) and displayed these messages:


May 22 21:59:04 ivoire com.apple.launchd[1] (com.apple.xpcd.F5010000-0000-0000-0000-000000000000[26487]): Exited: Killed: 9
May 22 21:59:04 ivoire kernel[0]: memorystatus_thread: idle exiting pid 26487 [xpcd]
May 22 22:04:32 ivoire com.apple.launchd.peruser.502[2211] (com.apple.cfprefsd.xpc.agent[26538]): Exited: Killed: 9
May 22 22:04:32 ivoire kernel[0]: memorystatus_thread: idle exiting pid 26538 [cfprefsd]
May 22 22:04:33 ivoire kernel[0]: (default pager): [KERNEL]: ps_select_segment - send HI_WAT_ALERT
May 22 22:04:34 ivoire kernel[0]: (default pager): [KERNEL]: ps_vstruct_transfer_from_segment - ABORTED
May 22 22:04:34 ivoire kernel[0]: (default pager): [KERNEL]: Failed to recover emergency paging segment
May 22 22:04:34 ivoire kernel[0]: macx_swapon SUCCESS
May 22 22:05:02 ivoire.paulbeard.org paul[26584]: swap in use = 4096, exceeds installed RAM (4096), last reboot was May 20 17:51 , recommend reboot

This — Failed to recover emergency paging segment — looks alarming. I doubt it is. It’s not new, in any case.

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