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Subject/proc/meminfo swap counter wraparound in 2.2
Hi there

Having put 8Gb of swap on one of our production database servers[1], I found
that "top", "free" et al report the amount of available swap space incorrectly.

This is because they all parse /proc/meminfo, and its counters seem to wrap
when they encounter very high numbers. The relevant bit is the totalswap
member of "struct sysinfo"

sean@lisa:~$ cat /proc/swaps
Filename Type Size Used Priority
/dev/rd/c0d2p1 partition 530104 41436 10
/usr/SWAPFILE1 file 1048568 56 2
/usr/local/SWAPFILE1 file 1048568 52 2
/usr/SWAPFILE2 file 1572856 0 3
/usr/local/SWAPFILE2 file 1572856 0 3
/var/SWAPFILE2 file 1572856 0 3
/home/SWAPFILE2 file 1572856 0 -6

sean@lisa:~$ cat /proc/meminfo
total: used: free: shared: buffers: cached:
Mem: 4125683712 2820616192 1305067520 0 82919424 232722432
Swap: 542777344 42541056 500236288
MemTotal: 4028988 kB
MemFree: 1274480 kB
MemShared: 0 kB
Buffers: 80976 kB
Cached: 227268 kB
BigTotal: 3111908 kB
BigFree: 1266988 kB
SwapTotal: 530056 kB
SwapFree: 488512 kB

sean@lisa:~$ uname -a
Linux lisa.sportingbet.com 2.2.19-6.2.7enterprise #1 SMP Thu Jun 14 07:34:12 EDT 2001 i686 unknown

As you can see, we are running redhat's "enterprise" 2.2.19 kernel.

I would be amazed if this bug were not also in the main 2.2.x tree. Is a fix
likely or even possible in 2.2 ?

Sean

[1]One of several changes to avoid random oracle 600 errors under heavy load.
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