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https://issues.apache.org/jira/browse/HBASE-13876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14581176#comment-14581176
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Elliott Clark commented on HBASE-13876:
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* tolerance should be configurable and I don't think that 0 is going to be the
correct value.
* line 141 compare them to tolerance.
* For line 140 - 154 It would be easier to reason about the percent if you
don't add them but rather compare them to tolerance
so instead of something like:
{code}if (percentChangeInEvictCount + percentChangeInFlushes > tolerance){code}
something like
{code}if ( precentChanceInEvictCount > 0 && percentChangeInEvictCount >
tolerance && precentChangeInFlushes < 0 && Math.abs(percentChangeInFlushes) >
tolerance){code}
* Need to make sure that no two calls to tune will ever run concurrently.
* Probably easier to have a variable like prevTuneDirection rather than using
the same variable for both meanings.
> 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, HBASE-13876.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 rare.
> 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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