Originally posted by: SystemAdmin

It appears that the vmo tunable parameter "page_steal_method" will have the default switched from "0" (as it is in 5.3) to "1" (as it will be in 6.1). Also, it appears that this parameter will be one of the "restricted tunables" in 6.1.

Has anyone made use of "page_steal_method=1" in a 5.3 environment? Any performance comparisons between "0" and "1" in either 5.3 or 6.1?

Many thanks!
#AIX-Forum

Originally posted by: MarkTaylor

The default == 1 in both 5.3 and 6.1

From the docs:

In AIX 5.3, the LRU algorithm can either use lists or the page frame table. Prior to AIX 5.3, the page frame table method was the only method available. The list-based algorithm provides a list of pages to scan for each type of segment.

The following is a list of the types of segments:

* Working
* Persistent
* Client
* Compressed

If WLM is enabled, there are lists for classes as well.
You can disable the list-based LRU feature and enable the original physical-address-based scanning with the page_steal_method parameter of the vmo command. The default value for the page_steal_method parameter is 1, which means that the list-based LRU feature is enabled and lists are used to scan pages. If the page_steal_method parameter is set to 0, the physical-address-based scanning is used. The value for the page_steal_method parameter takes effect after a bosboot and reboot.
Note: With list-based scanning, buckets that are specified with the lrubucket parameter are still used, but buckets can overlap on multiple lists and include a count of the number of pages that were scann
Rgds
Mark Taylor

Message was edited by: MarkTaylor
#AIX-Forum

Originally posted by: jvanibm

I've seen conflicting information on the page_steal_method defaults for 5.3... the current writeup in the 5.3 publib section:

List-based LRU

In AIX® 5.3, the LRU algorithm can either use lists or the page frame table. Prior to AIX 5.3, the page frame table method was the only method available. The list-based algorithm provides a list of pages to scan for each type of segment.

The following is a list of the types of segments:

* Working
* Persistent
* Client
* Compressed

If WLM is enabled, there are lists for classes as well.
You can disable the list-based LRU feature and enable the original physical-address-based scanning with the page_steal_method parameter of the vmo command. The default value for the page_steal_method parameter is 0, which means that the list-based LRU feature is enabled and lists are used to scan pages. If the page_steal_method parameter is set to 1, the physical-address-based scanning is used. The value for the page_steal_method parameter takes effect after a bosboot and reboot.
Note: With list-based scanning, buckets that are specified with the lrubucket parameter are still used, but buckets can overlap on multiple lists and include a count of the number of pages that were scanned.
Parent topic: VMM page replacement tuning
And in the 6.1 publib reference:

List-based LRU

In AIX® 5.3, the LRU algorithm can either use lists or the page frame table. Prior to AIX 5.3, the page frame table method was the only method available. The list-based algorithm provides a list of pages to scan for each type of segment.

The following is a list of the types of segments:

* Working
* Persistent
* Client
* Compressed

If WLM is enabled, there are lists for classes as well.
You can disable the list-based LRU feature and enable the original physical-address-based scanning with the page_steal_method parameter of the vmo command. The default value for the page_steal_method parameter is 1, which means that the list-based LRU feature is enabled and lists are used to scan pages. If the page_steal_method parameter is set to 0, the physical-address-based scanning is used. The value for the page_steal_method parameter takes effect after a bosboot and reboot.
Note: With list-based scanning, buckets that are specified with the lrubucket parameter are still used, but buckets can overlap on multiple lists and include a count of the number of pages that were scanned.
Parent topic: VMM page replacement tuning

From runs of vmo -L on a 5.3.8.6 system, the default for page_steal_method is listed as 0 (zero). What that means in 5.3 seems to be 'list-based', if I read the publib pages correctly. So it appears that 'list-based' is the default in 5.3 and 6.1; it's just signified by different default values.
#AIX-Forum

Originally posted by: MarkTaylor

The conflicting information you mention is probably because the tuning option was introduced as part of a TL .. by the looks of it was introduced in 5.3 TL10 which is why it is zero in TL8 .. can you change it at TL8 ? you will prob get an error ..

ref: http://www-01.ibm.com/support/docview.wss?uid=isg1IY59704

Rgds
Mark Taylor
#AIX-Forum

Originally posted by: MarkTaylor

Looking into this deeper, you are right .. "0" is physical based and "1" is list based on both 5.3 and 6.1, the default on 5.3 is physical "0" and on 6.1 is list based "1" .. the docs are incorrect, I rasied a pmr and IBM confirmed this.

HTH
Mark Taylor
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