From: Renison, Rick (rick.renison@EDS.COM)
Date: Mon May 19 2003 - 22:38:58 EDT
Both pinned and persistent memory are not swapped out.
Pinned memory takes up real memory. It is never swapped out or in. Real
memory is kept for it.
Persistent memory is memory that has real disk space, not needing swap out.
This is used for executable (text) code. It can always be re-read into
memory, since code is NOT self modifiable. It can, however, be discarded
(reused memory, but can always be read again from disk). This is why a
compile-link finds the disk space as in-use. This feature is used by AIX
itself.... only a portion of the swapper task is actually pinned in memory;
the rest is just persistent (let LRU algorithm handle it)... the pinned
stuff can read in the persistent code.
So, like you deduced, pinned persistent memory is used for:
a) bootstrap code, like the swapper task
b) really time critical code, where re-reading the program text segments
will affect the results.
...Rick
-----Original Message-----
From: Holger.VanKoll@SWISSCOM.COM [mailto:Holger.VanKoll@SWISSCOM.COM]
Sent: May 15, 2003 8:06 AM
To: aix-l@Princeton.EDU
Subject: Re: pinning persistent storage
Well,
I think a "pinned page" is a page that has to be kept in ram.
As long as its part of a working segment, thats equal to "not page out" or
"not swap out" (both terms are used within aix-docu).
So, the point of pinning persistent segments might be to allow fast
execution without loading pages from storage.
Those two processes where I noticed pinned persistent pages (hatsd and
shdaemon) are both time-critical.
This is all guessing, but sounds reasonable to me.
Anyway, if someone knows for sure, please post.
Regards,
Holger
-----Original Message-----
From: Van Koll Holger, IT-DCS-SES-UN
Sent: Thursday, May 15, 2003 12:06 PM
To: aix-l@Princeton.EDU
Subject: pinning persistent storage
Hello,
pinned memory is memory that is marked as "do not page out",
correct?
persistent storage will never be paged out, correct?
If both is correct, why are there some pinned pages of persistent
segments?
root@0-tvgicsc1 179# svmon -G
work pers clnt
pin 6740 172 0
root@0-tvgicsc1 180# svmon -S -f|grep -v "0 - -"
Vsid Esid Type Description Inuse Pin Pgsp Virtual Addr
Range
78dc - pers /dev/hd2:84132 181 172 - - 0..714
root@0-tvgicsc1 181# ncheck -i 84132 /dev/hd2
/dev/hd2:
84132 /sbin/rsct/bin/hatsd
or, on another system:
sbe12169 # svmon -G
work pers clnt lpage
pin 786299 5 0 0
sbe12169 # svmon -S -f|grep -v "0 - -"
Vsid Esid Type Description LPage Inuse Pin Pgsp
Virtual
4e0538 - pers /dev/hd2:10817 - 5 5 -
-
sbe12169 # ncheck -i 10817 /dev/hd2
/dev/hd2:
10817 /sbin/shdaemon
Regards,
Holger
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