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https://issues.apache.org/jira/browse/HDFS-15409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17149176#comment-17149176
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Danil Lipovoy commented on HDFS-15409:
--------------------------------------
I was surprised, but old (current) version shows better distribution:
{code:java}
public ShortCircuitCache getShortCircuitCache(Long idx) {
LOG.info("shortCircuitCache: " + (int) (idx % clientShortCircuitNum));
return shortCircuitCache[(int) (idx % clientShortCircuitNum)];
}
{code}
cat /var/log/hbase/hbase-cmf-hbase-REGIONSERVER-home.com.log.out |grep
"shortCircuitCache:"|awk '\{print $6}'| sort | uniq -c | sort -nr | awk
'\{printf "%-8s%s\n", $2, $1}'|sort
0 557207
1 545778
2 556965
It was the same test scenario. I agree, It looks strange, but I can't beat the
facts)
> Optimization Strategy for choosing ShortCircuitCache
> -----------------------------------------------------
>
> Key: HDFS-15409
> URL: https://issues.apache.org/jira/browse/HDFS-15409
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Lisheng Sun
> Assignee: Lisheng Sun
> Priority: Major
>
> When clientShortCircuitNum is 10, the probability of falling into each
> ShortCircuitCache is the same, while the probability of other
> clientShortCircuitNum is different.
> For example if clientShortCircuitNum is 3, when a lot of blockids of SSR are
> ***1, ***4, ***7， this situation will fall into a ShortCircuitCache.
> Since the real environment blockid is completely unpredictable, i think it is
> need to design a strategy which is allocated to a specific ShortCircuitCache.
> This should improve performance even more.
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