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ramkrishna.s.vasudevan commented on HBASE-13082: ------------------------------------------------ But again if handling flushes is a problem then resetting the heap should be done at any case. > Coarsen StoreScanner locks to RegionScanner > ------------------------------------------- > > Key: HBASE-13082 > URL: https://issues.apache.org/jira/browse/HBASE-13082 > Project: HBase > Issue Type: Bug > Reporter: Lars Hofhansl > Assignee: ramkrishna.s.vasudevan > Attachments: 13082-test.txt, 13082-v2.txt, 13082-v3.txt, > 13082-v4.txt, 13082.txt, 13082.txt, HBASE-13082.pdf, HBASE-13082_1_WIP.patch, > HBASE-13082_2_WIP.patch, HBASE-13082_3.patch, HBASE-13082_4.patch, gc.png, > gc.png, gc.png, hits.png, next.png, next.png > > > Continuing where HBASE-10015 left of. > We can avoid locking (and memory fencing) inside StoreScanner by deferring to > the lock already held by the RegionScanner. > In tests this shows quite a scan improvement and reduced CPU (the fences make > the cores wait for memory fetches). > There are some drawbacks too: > * All calls to RegionScanner need to be remain synchronized > * Implementors of coprocessors need to be diligent in following the locking > contract. For example Phoenix does not lock RegionScanner.nextRaw() and > required in the documentation (not picking on Phoenix, this one is my fault > as I told them it's OK) > * possible starving of flushes and compaction with heavy read load. > RegionScanner operations would keep getting the locks and the > flushes/compactions would not be able finalize the set of files. > I'll have a patch soon. -- This message was sent by Atlassian JIRA (v6.3.4#6332)