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https://issues.apache.org/jira/browse/HBASE-10263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13865119#comment-13865119
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Feng Honghua commented on HBASE-10263:
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Before this jira, a rough performance comparison estimate can be like
this(within a single regionserver): suppose the total size of in-memory data
served by this regionserver is M, total size of non-in-memory data is N, the
block cache size is C, then C/4 is for in-memory data, 3*C/4 is for
non-in-memory data, the cache hit ratio of random read for in-memory data is
C/(4*M), cache hit ratio for non-in-memory data is 3*C/(4*N), so the
performance of random read to these two kinds of data is equal when C/(4*M) ==
3*C/(4*N), so:
1. when M > N/3, in-memory table random read performance is worse than ordinary
table;
2. when M == N/3, in-memory table random read performance is equal to ordinary
table;
2. when M < N/3, in-memory table random read performance is better than
ordinary table;
> 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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