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https://issues.apache.org/jira/browse/HDFS-5810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13897159#comment-13897159
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Colin Patrick McCabe commented on HDFS-5810:
--------------------------------------------
I uploaded a new version which is rebased on trunk. It changes the "caller
strings" for dumping stack traces, uses
{{dfs.client.read.shortcircuit.streams.cache.size}} as an upper bound on the
size of both mmapped and non-mmapped replicas, and uses {{TimeUnit}} for time
conversions.
I changed the handling of {{outstandingMmapCount}} a little bit. Although we
still track this stat, we don't try to cap the number of outstanding mmaps.
That is up to the caller code, not to us. This is similar to how we handle
opening new FDs in general... we do it on request, no matter how many existing
FDs there are. Only when something is returned to the cache do we apply the
limits.
> Unify mmap cache and short-circuit file descriptor cache
> --------------------------------------------------------
>
> Key: HDFS-5810
> URL: https://issues.apache.org/jira/browse/HDFS-5810
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Affects Versions: 2.3.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-5810.001.patch, HDFS-5810.004.patch,
> HDFS-5810.006.patch, HDFS-5810.008.patch, HDFS-5810.015.patch,
> HDFS-5810.016.patch, HDFS-5810.018.patch, HDFS-5810.019.patch
>
>
> We should unify the client mmap cache and the client file descriptor cache.
> Since mmaps are granted corresponding to file descriptors in the cache
> (currently FileInputStreamCache), they have to be tracked together to do
> "smarter" things like HDFS-5182.
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