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https://issues.apache.org/jira/browse/HBASE-10263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13862144#comment-13862144
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Feng Honghua commented on HBASE-10263:
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[[email protected]]:
bq.Is the above variable used(inMemoryForceMode) ?
==> No, they(together with single/multi/memory factors) are not used. There is
a historical reason for these variables here: this flag(and other 3 factors)
will be read from *conf* passed as parameter in LruBlockCache constructor, in
0.94.3(our internal branch) there is a INFO log for max-size before
constructing the LruBlockCache, and I added these
'forceMode/single/multi/memory' info in that INFO log as well, they are used
just for info purpose, but this INFO log in CacheConfig.java doesn't exist in
trunk code(it's removed), and I forgot to remove these four just-for-info
variables accordingly. *It won't affect correctness*. Thanks for point this out
:-)
> 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
> Reporter: Feng Honghua
> Assignee: Feng Honghua
> Attachments: HBASE-10263-trunk_v0.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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