Summary:
This patch fixes two issues in DBTest.ApproximateMemoryUsage:
- It was possible that a flush happened between getting the two properties in
Phase 1, resulting in different numbers for the properties and failing the
assertion. This is fixed by waiting for the flush to finish before getting
the properties.
- There was a similar issue in Phase 2 and additionally there was an issue that
rocksdb.size-all-mem-tables was not monotonically increasing because it was
possible that a flush happened just after getting the properties and then
another flush just before getting the properties in the next round. In this
situation, the reported memory usage decreased. This is fixed by forcing a
flush before getting the properties.
Note: during testing, I found that kFlushesPerRound does not seem very
accurate. I added a TODO for this and it would be great to get some input on
what to do there.
Test Plan:
The first issue can be made more likely to trigger by inserting a
`usleep(10000);` between the calls to GetIntProperty() in Phase 1.
The second issue can be made more likely to trigger by inserting a
`if (r != 0) usleep(10000);` before the calls to GetIntProperty() and a
`usleep(10000);` after the calls.
Then execute make db_test && ./db_test --gtest_filter=DBTest.ApproximateMemoryUsage
Reviewers: rven, yhchiang, igor, sdong, anthony
Reviewed By: anthony
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D45675
e853191c17