|Title||Accounting overheads are too high on mark & sweep pools|
|Assigned user||Richard Brooksby|
|Description||Changelist 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.|
|Analysis||1. 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.
|Evidence||LOSegStruct, AMSSegStruct, and AWLSegStruct|
|Created by||Richard Brooksby|
|Created on||2016-04-29 08:54:37|
|Last modified by||Gareth Rees|
|Last modified on||2016-09-13 10:35:28|
|History||2016-04-29 RB Created.|