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https://issues.apache.org/jira/browse/HBASE-10263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13864982#comment-13864982
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Feng Honghua commented on HBASE-10263:
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bq.Any chance you can post some more detailed performance numbers around this
new preemptive mode? Any commentary from your profiling session as to why the
existing logic caused such unexpected poor performance? If it's broken always,
for everyone, we should follow Good stack's advice and tear out the broken
logic, enabling forceInMemory by default.
Sure, I ever did a series of performance comparison tests for this patch
several months ago(it's based on our internal 0.94.3 branch), let me copy the
test result from our wiki page to here, wait...
> make LruBlockCache single/multi/in-memory ratio user-configurable and provide
> preemptive mode for in-memory type block
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-10263
> URL: https://issues.apache.org/jira/browse/HBASE-10263
> Project: HBase
> Issue Type: Improvement
> Components: io
> Reporter: Feng Honghua
> Assignee: Feng Honghua
> Attachments: HBASE-10263-trunk_v0.patch, HBASE-10263-trunk_v1.patch,
> HBASE-10263-trunk_v2.patch
>
>
> currently the single/multi/in-memory ratio in LruBlockCache is hardcoded
> 1:2:1, which can lead to somewhat counter-intuition behavior for some user
> scenario where in-memory table's read performance is much worse than ordinary
> table when two tables' data size is almost equal and larger than
> regionserver's cache size (we ever did some such experiment and verified that
> in-memory table random read performance is two times worse than ordinary
> table).
> this patch fixes above issue and provides:
> 1. make single/multi/in-memory ratio user-configurable
> 2. provide a configurable switch which can make in-memory block preemptive,
> by preemptive means when this switch is on in-memory block can kick out any
> ordinary block to make room until no ordinary block, when this switch is off
> (by default) the behavior is the same as previous, using
> single/multi/in-memory ratio to determine evicting.
> by default, above two changes are both off and the behavior keeps the same as
> before applying this patch. it's client/user's choice to determine whether or
> which behavior to use by enabling one of these two enhancements.
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