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https://issues.apache.org/jira/browse/MAPREDUCE-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033105#comment-13033105
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Owen O'Malley commented on MAPREDUCE-2494:
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I was also surprised when I walked through the code and saw that it was
deleting all currently unused objects.
I think a straight LRU with a goal percentage of the threshold makes sense. For
a first pass of this, I think the object's size should be ignored until we
understand better how it interacts with the rest of the system.
So something like:
{code}
when (free space on partition < free-limit or
disk usage of dist cache > cache-limit) and
time since last purge > 10 minutes:
purge LRU unused objects to reach goal size of cache-limit*cache-usage-goal
{code}
Does that make sense?
> Make the distributed cache delete entires using LRU priority
> ------------------------------------------------------------
>
> Key: MAPREDUCE-2494
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2494
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: distributed-cache
> Affects Versions: 0.21.0
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
>
> Currently the distributed cache will wait until a cache directory is above a
> preconfigured threshold. At which point it will delete all entries that are
> not currently being used. It seems like we would get far fewer cache misses
> if we kept some of them around, even when they are not being used. We should
> add in a configurable percentage for a goal of how much of the cache should
> remain clear when not in use, and select objects to delete based off of how
> recently they were used, and possibly also how large they are/how difficult
> is it to download them again.
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