AIX : 0 pages swappes - AIX

hmaiida · #1 (**permalink**) 04-25-2008

hi admin,

How to fix a problem of alerts of this type?:

"0 pages swapped"

thanks

bakunin · #2 (**permalink**) 04-25-2008

What has issued this alert? Where did it appear?

Please post the output of "lsps -a" and "lsattr -El mem0" to further examine the problem.

bakunin

hmaiida · #3 (**permalink**) 04-25-2008

it's a patrol alert!

what can i do when i see with topas that i have faults of 7000 and 0 in PsgpIn and PsgpOut with some activity on PageIn and PageOut.
Is it normal situation?

thanks for reply

Shrek · #4 (**permalink**) 04-28-2008

Hey hmaiida,

High paging faults is known as thrashing in UNIX enviroments and it's not a normal situation at all. In AIX there are some parameters you can set in order to prevent this behavior. Parameters like maxperm|minperm|maxclient in order to free real memory for specific use of file pages.
Before you go tuning anything, call IBM's AIX Support and talk to them regarding this.

Do post the output of below commands:-

Code:

#lsps -a 

#vmo -a | egrep "maxperm|minperm|maxclient"

And by the way whats your real memory size?

bakunin · #5 (**permalink**) 04-28-2008

Here is a quick-and-dirty first estimation of a possible memory shortage:

Issue "svmon -G" and compare the numbers marked bold in the following example:

Code:

               size      inuse       free        pin    virtual
memory      1572864    1557689      15175     389150    1311648
pg space    2097152     427109

               work       pers       clnt
pin          388839          0        311
in use       977383          0     580306

PageSize   PoolSize      inuse       pgsp        pin    virtual
s   4 KB          -    1448041     427109     318814    1202000
m  64 KB          -       6853          0       4396       6853

The memory is measured in 4k-pages here. The ~1.5 millions means 6GB real memory therefore. Then compare the "inuse" number with the "virtual" number and if the "virtual" number is significantly higher the difference is about the memory you are lacking. i.e 1.5 mio "inuse" versus 2 mio "virtual" means you need to add about 500k x 4k ~= 2GB memory.

Again, this is only a QUICK and ROUGH estimation, not an in-depth analysis. Such an analysis might well reveal a different number.

Another place to look is "vmstat -v", especially for machines with a high I/O-workload. Have a look at the lines marked bold in the following example:

Code:

              1572864 memory pages
              1487316 lruable pages
                15273 free pages
                    1 memory pools
               389150 pinned pages
                 80.0 maxpin percentage
                 20.0 minperm percentage
                 80.0 maxperm percentage
                 37.0 numperm percentage
               551288 file pages
                  0.0 compressed percentage
                    0 compressed pages
                 37.0 numclient percentage
                 80.0 maxclient percentage
               551288 client pages
                    0 remote pageouts scheduled
                17676 pending disk I/Os blocked with no pbuf
               151067 paging space I/Os blocked with no psbuf
                 2484 filesystem I/Os blocked with no fsbuf
                    0 client filesystem I/Os blocked with no fsbuf
               474712 external pager filesystem I/Os blocked with no fsbuf
                    0 Virtualized Partition Memory Page Faults
                 0.00 Time resolving virtualized partition memory page faults

These are totals therefore repeat that command every minute or so and observe the change in these numbers. If they grow at a very fast rate the system has not enough memory to spare for buffered disk-I/O. Probably you will notice a very bad filesystem performance because of this. Usually this is due to a very constrained memory situation and while you might somewhat deescalate the situation by some tuning you will probably need more memory to solve tis problem.

I hope this helps.

bakunin

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