Date: Wed, 30 Nov 2011 12:39:10 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: <freebsd-hackers@freebsd.org> Subject: Invalid memory stats from vmstat and sysctl vm.vmtotal? Message-ID: <547298A3C38F407887E1AAAAC487DF6D@multiplay.co.uk>
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We're seeing some impossible memory usage stats reported on machines
here from vmstat and sysctl vm.vmtotal.
We have machines reporting to be using 31GB total when they only have
8GB physical and are not using any swap.
Here's an output from one of our machines:-
vmstat -c 2 -w 1 -n 0
procs memory page faults cpu
r b w avm fre flt re pi po fr sr in sy cs us sy id
0 0 0 31768M 2112M 586 0 0 0 421 0 106 270 569 0 6 94
0 0 0 31768M 2112M 2 0 0 0 0 0 370 8139 3996 0 1 99
The raw output is:-
vmstat -c 2 -w 1 -n 0 -H
procs memory page faults cpu
r b w avm fre flt re pi po fr sr in sy cs us sy id
0 0 0 32530228 2162524 586 0 0 0 421 0 106 270 569 0 6 94
0 0 0 32530228 2162524 2 0 0 0 0 0 286 8234 4347 0 1 99
Top shows:-
last pid: 6665; load averages: 0.00, 0.00, 0.01 up 80+01:24:12 09:35:28
1893 processes:1 running, 1892 sleeping
CPU: 0.0% user, 0.0% nice, 0.3% system, 0.0% interrupt, 99.7% idle
Mem: 3754M Active, 84M Inact, 1976M Wired, 4K Cache, 2109M Free
Swap: 4096M Total, 4096M Free
sysctl vm.vmtotal
vm.vmtotal:
System wide totals computed every five seconds: (values in kilobytes)
===============================================
Processes: (RUNQ: 1 Disk Wait: 0 Page Wait: 0 Sleep: 1893)
Virtual Memory: (Total: 1106403532K Active: 32540260K)
Real Memory: (Total: 4563648K Active: 3921644K)
Shared Virtual Memory: (Total: 19976K Active: 16396K)
Shared Real Memory: (Total: 9040K Active: 8436K)
Free Memory Pages: 2161740K
As mentioned this machine has 8GB of ram and according to both top and
swapinfo is using no swap at all
>From dmesg:-
real memory = 8589934592 (8192 MB)
avail memory = 8255553536 (7873 MB)
swapinfo
Device 1K-blocks Used Avail Capacity
/dev/gptid/09f211f7-39ce-11e0-8 4194304 0 4194304 0%
uname -a
FreeBSD test 8.2-RELEASE FreeBSD 8.2-RELEASE #2: Thu Mar 24 17:28:55 UTC 2011 root@test:/usr/obj/usr/src/sys/MULTIPLAY amd64
sysctl hw.pagesize
hw.pagesize: 4096
It looks like it may be out by a factor of 4, possibly due to the fact
the its a 4k page size not 1k as indicated by the vmstat man page:-
memory Information about the usage of virtual and real memory. Virtual
pages (reported in units of 1024 bytes) are considered active if
they belong to processes which are running or have run in the
last 20 seconds.
avm active virtual pages
fre size of the free list
Totalling up RSS from ps axo "rss" gives a total in the region of that if
the vm stats are out by a factor of 4, in this case it should be: 8132557
which is 7.75GB a much more realistic value.
Am I totally missing something or is there problem here?
Regards
Steve
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