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Todd Lipcon updated HBASE-3455: ------------------------------- Attachment: mslab-3.txt Oops, missed one test change before. This patch should be good to go. I tested under heavy load (95% write, 5% increment, large working set to trigger block cache churn) on a cluster for about 16 hours, no full GCs at all in 8G heap with CMS. But it's still off by default because of the worrisome theoretical possibilities with upsert. > Heap fragmentation in region server > ----------------------------------- > > Key: HBASE-3455 > URL: https://issues.apache.org/jira/browse/HBASE-3455 > Project: HBase > Issue Type: Brainstorming > Components: performance, regionserver > Reporter: Todd Lipcon > Priority: Critical > Attachments: collapse-arrays.patch, HBasefragmentation.pdf, > icv-frag.png, mslab-1.txt, mslab-2.txt, mslab-3.txt, parse-fls-statistics.py, > with-kvallocs.png > > > Stop-the-world GC pauses have long been a problem in HBase. "Concurrent mode > failures" can usually be tuned around by setting the initiating occupancy > fraction low, but eventually the heap becomes fragmented and a promotion > failure occurs. > This JIRA is to do research/experiments about the heap fragmentation issue > and possible solutions. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.