MPS issue job004024

TitleAccounting overheads are too high on mark & sweep pools
Assigned userRichard Brooksby
DescriptionChangelist 185888 introduced double-entry book-keeping to every segment in the LO, AWL, and AMS pool classes, resulting in a four word overhead on every segment. This is too high.
Analysis1. Define and justify "too high".
2. Each account in the segment takes up a whole 64-bit word, but the information it stores is usually only 9 bits long, though that depends on the size of the segment. Can it be compressed?
3. The accounts are redundant (being double-entry) but they're also double-entry at the level of the generation, so this may be excessive redundancy.
4. The accounts are only used for two things: to feed in to the generation accounts, and to speed up the allocation search. The allocation needs reform, and then perhaps they can be eliminated a the segment level.
How foundinspection
EvidenceLOSegStruct, AMSSegStruct, and AWLSegStruct
Created byRichard Brooksby
Created on2016-04-29 08:54:37
Last modified byGareth Rees
Last modified on2016-09-13 10:35:28
History2016-04-29 RB Created.