2 ms·
The referenced paper is a bit vague about this: An alternative to side bitmaps is a bytemap, a bytegrained data structure on the side. Bytemaps trade an 8× spa
by danieldk 11y ago
The referenced paper is a bit vague about this:
An alternative to side bitmaps is a bytemap, a bytegrained
data structure on the side. Bytemaps trade an 8×
space overhead to avoid synchronizing on each set operation
(if we assume support for atomic byte-grained stores).
I think the idea is that, since a bytemap is less dense, two cores less frequently access the same cache lines, leading to fewer invalidations. Though, I wonder if it pays off, since it also gives less locality.
- yxhuvud 11y agoNo, it is referring to the fact that the least unit that can be written to memory isn't a bit but a byte. To write a bit the whole byte must be read, modified and then written back.
- danieldk 11y agoSure, but in both cases if a mark needs to be changed 'the whole byte needs to be read modified and written back', bitmaps or bytemaps.