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https://issues.apache.org/jira/browse/GEODE-9033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17318366#comment-17318366
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Mark Hanson commented on GEODE-9033:
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After further investigating this situation with Darrel, it seems that the only
viable path is to introduce a new Object to synchronize on when writing or
reading the value or version stamp in a versioned region entry. In a
non-versioned region entry, this is not necessary. Using volatile seem to have
to clear safe way to solve this problem. Hence synchronizing on a new object.
The problem with that is that the footprint of a region entry would grow by the
size of an Object.
> client read operations should not be blocked by a write operation
> -----------------------------------------------------------------
>
> Key: GEODE-9033
> URL: https://issues.apache.org/jira/browse/GEODE-9033
> Project: Geode
> Issue Type: Improvement
> Components: client/server
> Affects Versions: 1.1.0
> Reporter: Darrel Schneider
> Assignee: Mark Hanson
> Priority: Major
> Labels: GeodeOperationAPI, performance
>
> Client read operations currently will be blocked by a write operation that is
> in progress.
> This is caused by the write operation holding a synchronization on the
> RegionEntry and LocalRegion.getDeserializedValue synchronizing the
> RegionEntry with clientEvent is not null in order to atomically obtain both
> the entry's value and version.
> The read code in LocalRegion that causes this is:
> {code:java}
> synchronized (regionEntry) {
> // value & version must be obtained atomically
>
> clientEvent.setVersionTag(regionEntry.getVersionStamp().asVersionTag());
> value = getDeserialized(regionEntry, updateStats,
> disableCopyOnRead,
> preferCachedDeserializable, retainResult);
> }
> {code}
> To fix this it may be possible to change the write operations to synchronize
> on something else while changing both the value and version (but not while
> doing anything else). Then the read code can sync on that new Object and not
> the RegionEntry instance.
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