vmstat memory variables

vmstat memory variables

Post 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.

 
 
 

vmstat memory variables

Post 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.


 
 
 

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