Very Computer

by **L.Ra** » Sat, 01 May 1999 04:00:00

Can someone please explain exactly what the "avm" and "fre" field in
"vmstat" is? I've read that "fre" doesn't really represent the amount
of free virtual memory, and I shouldn't be concerned when it gets
low... what does it represent then? And exactly how is the amount of
virtual memory derived?

kthr memory page faults cpu
----- ----------- ------------------------ ------------ -----------
r b avm fre re pi po fr sr cy in sy cs us sy id wa
0 0 420519 66772 0 0 0 0 0 0 166 215 113 1 1 92 6
0 2 420519 66772 0 0 0 0 0 0 1976 9106 1358 0 0 99 0
0 2 420519 66772 0 0 0 0 0 0 1977 8937 1352 0 0 99 0
0 2 420519 66772 0 0 0 0 0 0 1955 9323 1348 0 0 99 0
0 2 420519 66772 0 0 0 0 0 0 1960 8849 1346 0 0 99 0

Above is an excert from the vmstat command run on a raven with 5gb of
RAM. The available memory is 420519 pages, which according to the man
pages is 1,72 GB (4019 bytes * 420519). Shouldn't I have MORE
available memory than real memory? My concern is that the system
isn't using the entire 5GB of real memory.

To confuse the matter, running monitor shows the following memory
stats:

Memory Real Virtual
free 260 MB 1642 MB
procs 4192139 MB 405 MB
files 2927 MB
total 1024 MB 2048 MB

Again, the total is much less then the actual memory.

Any help/explainations would be greatly appreciated.

by **L.Ra** » Wed, 05 May 1999 04:00:00

Thanks. Those website pages were really helpful.

On Fri, 30 Apr 1999 19:10:12 -0400, Flemming Josephsen

>This is really well described in the various AIX books. There are some
>sections on the rs6k website that deals with 'understanding <whatever>
>...'

>Also, the performance tuning guide is a good source of info.

>avm = Active Virtual Memory

>fre = free pages

>and yes .. the fre column is kinda important in the sense that if the
>number drops to 120 or less you are going to see some serious 'panic' to
>free up memory

>One thing you might want to check since you have 5 GB of RAM, assuming
>you are running 4.3.2 is that the networking parameter thewall default
>to 1 GB of RAM... also check vmtune for the -p and -P. You might want
>to take those down to 10 and 20 percent respectively.

>If you want to know how much memory you system can see, then try this:

>expr `bootinfo -r` / 1024

>> Can someone please explain exactly what the "avm" and "fre" field in
>> "vmstat" is? I've read that "fre" doesn't really represent the amount
>> of free virtual memory, and I shouldn't be concerned when it gets
>> low... what does it represent then? And exactly how is the amount of
>> virtual memory derived?

>> kthr memory page faults cpu
>> ----- ----------- ------------------------ ------------ -----------
>> r b avm fre re pi po fr sr cy in sy cs us sy id wa
>> 0 0 420519 66772 0 0 0 0 0 0 166 215 113 1 1 92 6
>> 0 2 420519 66772 0 0 0 0 0 0 1976 9106 1358 0 0 99 0
>> 0 2 420519 66772 0 0 0 0 0 0 1977 8937 1352 0 0 99 0
>> 0 2 420519 66772 0 0 0 0 0 0 1955 9323 1348 0 0 99 0
>> 0 2 420519 66772 0 0 0 0 0 0 1960 8849 1346 0 0 99 0

>> Above is an excert from the vmstat command run on a raven with 5gb of
>> RAM. The available memory is 420519 pages, which according to the man
>> pages is 1,72 GB (4019 bytes * 420519). Shouldn't I have MORE
>> available memory than real memory? My concern is that the system
>> isn't using the entire 5GB of real memory.

>> To confuse the matter, running monitor shows the following memory
>> stats:

>> Memory Real Virtual
>> free 260 MB 1642 MB
>> procs 4192139 MB 405 MB
>> files 2927 MB
>> total 1024 MB 2048 MB

>> Again, the total is much less then the actual memory.

>> Any help/explainations would be greatly appreciated.

Very Computer

vmstat memory variables

vmstat memory variables

vmstat memory variables