| Title: | VM Arena's segment placement policy could be improved. |
| Status: | open |
| Priority: | essential |
| Assigned user: | Richard Brooksby |
| Organization: | Ravenbrook |
| Description: | VM 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 generations). (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. |
| Analysis: | Description contains some analysis. |
| How found: | unknown |
| Evidence: | I just know. |
| Observed in: | 1.108.0 |
| Created by: | David Jones |
| Created on: | 2007‑09‑07 14:59:39 |
| Last modified by: | Gareth Rees |
| Last modified on: | 2013‑03‑19 11:56:40 |
| History: | 2007-09-06 DRJ Created 2013-03-19 GDR Assigned to RB. |
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