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PagingSpace

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Operating Systems AIX PagingSpace
# 1  
Old 10-01-2010
PagingSpace
Hi,

From the nmon, what is the PageSpace %used ?

Also I see Page Faults value are high. Is this mean the system is having memory constraints?

Code:
vmstat -v
              3948544 memory pages
              3743179 lruable pages
                61955 free pages
                    4 memory pools
               793274 pinned pages
                 80.0 maxpin percentage
                  3.0 minperm percentage
                 90.0 maxperm percentage
                  7.4 numperm percentage
               278545 file pages
                  0.0 compressed percentage
                    0 compressed pages
                  7.4 numclient percentage
                 90.0 maxclient percentage
               278545 client pages
                    0 remote pageouts scheduled
                 1249 pending disk I/Os blocked with no pbuf
               901109 paging space I/Os blocked with no psbuf
                 2484 filesystem I/Os blocked with no fsbuf
                    1 client filesystem I/Os blocked with no fsbuf
               866061 external pager filesystem I/Os blocked with no fsbuf
                    0 Virtualized Partition Memory Page Faults
                 0.00 Time resolving virtualized partition memory page faults



Page Faults    7001.4




vmstat 1

System configuration: lcpu=8 mem=15424MB

kthr    memory              page              faults        cpu    
----- ----------- ------------------------ ------------ -----------
 r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa
 3  0 3593316  3960   0   0   0 2128 23980   0 197 2922 3352 50  2 40  7
 3  0 3593318  3849   0   0   0 2692 10686   0 215 2810 3299 50  3 36 11
 4  0 3593315  4000   0   0   0 2696 6484   0 190 2785 3384 50  3 37 10
 4  0 3593309  3892   0   0   0 2441 5700   0 206 2664 3342 51  3 38  9
 4  0 3593308  4040   0   0   0 2698 6751   0 208 3021 3372 50  2 37 11
 3  0 3593309  5973   0   0   0 4243 11459   0 220 208901 4314 55  7 31  7

Moderator's Comments:
Mod Comment Having 16 posts already you should be familiar using code tags.
Last edited by zaxxon; 10-01-2010 at 03:51 AM..
# 2  
Old 10-01-2010
Quote:
From the nmon, what is the PageSpace %used ?
This shows similar output to
Code:
lsps -a

and just how much percent of available paging space is being used. What does lsps -a show on your system?


Quote:
Also I see Page Faults value are high. Is this mean the system is having memory constraints?
No. A Page Fault just says, that the requested data is currently not in memory and has to be read from disk. AIX is caching files in RAM, but if data is requested and not already in the cache, it has to be read from where it resides. So something very normal and nothing to worry about.

Looking at the vmstat, there seems to be no problem with your system at the time of the vmstat output taken. If you had actually memory problems, there would be non-zero values showing up in the columns for pi and po, which is reading from and writing to Paging Space. Though this is just a short snapshot. To see if there is paging eventually you might have to monitor it over a longer time, since there is also some
Code:
              901109 paging space I/Os blocked with no psbuf


Code:
               866061 external pager filesystem I/Os blocked with no fsbuf

This maybe no biggie but could be tried to avoid by increasing j2_dynamicBufferPreallocation - if it doesn't work you might also consider to increase j2_nBufferPerPagerDevice. For values, behaviour (dynamic) etc. you might want to have a look into the man page of ioo for those 2 parameters.


By the way - for a more tidier view of the columns of vmstat, you can use the -w switch so values will be indented accordingly to the heading.
Last edited by zaxxon; 10-01-2010 at 04:25 AM.. Reason: rephrasing, corrections
# 3  
Old 10-01-2010
your scan to free ratio is rather high - so you could use a few more gig of memory even though your computational memory value is not exceeding the amount of physical memory you have. Still you are using well over 14 GB on a system that only has 15 GB - IBM still recommends to keep the amount of computational memory in a range between 70 and 80% for best performance. If you start doing that, your scan to free ratio which is slowing down performance as well if its high will go down.

Kind regards
zxmaus
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