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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13876) Improving performance of HeapMemoryManager
Date Wed, 10 Jun 2015 23:19:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14581217#comment-14581217

Ted Yu commented on HBASE-13876:

bq. but at the same time we have very huge decrease in cache misses

Two percentages are maintained: change in eviction count and change in cache misses.
+        if (percentChangeInEvictCount + percentChangeInFlushes > tolerance) {
Did you intend to use percentChangeInMisses in the above check ?

> Improving performance of HeapMemoryManager
> ------------------------------------------
>                 Key: HBASE-13876
>                 URL: https://issues.apache.org/jira/browse/HBASE-13876
>             Project: HBase
>          Issue Type: Improvement
>          Components: hbase, regionserver
>    Affects Versions: 2.0.0, 1.0.1, 1.1.0, 1.1.1
>            Reporter: Abhilash
>            Assignee: Abhilash
>            Priority: Minor
>         Attachments: HBASE-13876-v2.patch, HBASE-13876-v3.patch, HBASE-13876-v4.patch,
> I am trying to improve the performance of DefaultHeapMemoryTuner by introducing some
more checks. The current checks under which the DefaultHeapMemoryTuner works are very rare
so I am trying to weaken these checks to improve its performance.
> Check current memstore size and current block cache size. If we are using less than 50%
of currently available block cache size  we say block cache is sufficient and same for memstore.
This check will be very effective when server is either load heavy or write heavy. Earlier
version just waited for number of evictions / number of flushes to be zero which are very
> Otherwise based on percent change in number of cache misses and number of flushes we
increase / decrease memory provided for caching / memstore. After doing so, on next call of
HeapMemoryTuner we verify that last change has indeed decreased number of evictions / flush
( combined). I am doing this analysis by comparing percent change (which is basically nothing
but normalized derivative) of number of evictions and number of flushes during last two periods.
The main motive for doing this was that if we have random reads then we will be having a lot
of cache misses. But even after increasing block cache we wont be able to decrease number
of cache misses and we will revert back and eventually we will not waste memory on block caches.
This will also help us ignore random short term spikes in reads / writes.

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