MPS issue job001708

TitleVM Arena's segment placement policy could be improved.
Assigned userRichard Brooksby
DescriptionVM Arena's segment placement policy could be improved.

Currently policy is to consider a series of zone subsets in a priority
order. This series is based on a number of factors, but including the
generation's zone set preference (its genZoneSet) and the (arena wide)
blacklist. Where P is the genZoneSet, F is the free zones, B is the
blacklist, and E is everything. Current algorithm prefers in the
following order:
  - P - B
  - P u (F-B)
  - not B
  - E

In the case where multiple generations share a zone in their genZoneSet
(which is a bad thing, but it happens) it would be better to avoid
zones used by other generations. If O is the set of zones preferred by
other generations then we should consider the following sets:
  - P - O - B
  - then as before (so prioritise zones that are not used by other

(this algorithm is implemented in pagesFindFreeWithSegPref)

Implementing the O step means that over time generations will tend to
avoid zones shared by other generations and eventually (if job001707 is
resolved) their genZoneSets can be reduced so as to avoid sharing zones
between generations.

This part of the algorithm needs making clearer in any case.
AnalysisDescription contains some analysis.
How foundunknown
EvidenceI just know.
Observed in1.108.0
Created byDavid Jones
Created on2007-09-07 14:59:39
Last modified byRichard Brooksby
Last modified on2013-06-16 07:22:35
History2007-09-06 DRJ Created
2013-03-19 GDR Assigned to RB.
2013-06-16 RB Downgraded to "nice" as there is no evidence that this is affecting anyone (see job003499).