| Title | MRG segments needlessly set the write barrier |
| Status | closed |
| Priority | optional |
| Assigned user | Gareth Rees |
| Organization | Ravenbrook |
| Description | MRG segments are never handed out to the mutator and so should never need to set the write barrier. But MRGSeg inherits from GCSeg, which sets the write barrier (see gcSegSyncWriteBarrier). This results in needless memory protection operations and failed assertions in finalization tests with deep checking (see job004030). |
| Analysis | Since MRG segments are never given to the mutator, the MPS doesn't need to use the write barrier to maintain the per-segment summary: instead, it could maintain the summary "by hand" using ArenaPoke. The segment class hierarchy should be finer grained: the GCSeg class should not implement the write barrier, and then pools can use a MutatorGCSeg subclass that implements the write barrier. |
| How found | inspection |
| Evidence | None |
| Created by | Gareth Rees |
| Created on | 2018-06-18 11:04:56 |
| Last modified by | Gareth Rees |
| Last modified on | 2018-07-05 16:29:04 |
| History | 2018-06-18 GDR Created. |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 194453 | closed | 2018-07-05 16:28:15 | Gareth Rees | Merge branch/2018-06-18/mrgseg into the master sources. |