Pgspgin/Pgspgout vs Pagein/Pageout

[needabiggerboat]

Am using Topas/Performance Aide to investigate performance degradation. Read man page for operational definitions for pagein/pageout and pgspgin/pgspgout but am still confused. Can not get a decent explanation from web or colleagues on difference between paging and swapping on Aix.

 

[letis]

hello,

I agree AIX doc is sometimes confusing when talking about performance metrics ...

In topas :
PgspIn = 4k blocs readem from PAGING space
PgspOut = 4 blocs writtent to PAGING space
PageIn = 4 blocs readen from Filesystems AND/OR paging space
PageOut = 4k blocks writtent to filesystems AND/OR paging space

Therefore, PgspIn is a subset from PageIn, and PgspOut is a subset from PageOut.

Make an experience (as root, and you muste have at least 40 MB free in / ) :
dd if=/dev/hdisk0 of=/my_file bs=4096 count=10000

and monitor with topas what'is heppening (PageIn/Out change but not PgspIn/Out).

If AIX 5.2, you can use :
vmstat -I 1

and look at the fi/fo columns, which represent what readen from / written to filesystems, while pi/po are 4k blocks read from / written to paging space.

regards

 

[needabiggerboat]

Good idea about using vmstat.

Page transfer to/from paging space is clearly indicative of a performance threat (e.g. box is swapping).

Does filesystem page transfer occur within RAM only?. It occurs a lot, and I know I'm less concerned about it wrt performance, but I don't know why.

Tx for responding. I'm a capacity analyst and should know why I do what I do!