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https://issues.apache.org/jira/browse/OAK-4635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15484257#comment-15484257
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Michael Dürig edited comment on OAK-4635 at 9/12/16 2:54 PM:
-------------------------------------------------------------
To address the OOME issue we have seen while evaluating this approach with the
OAK-4635-6 branch I suggest to
* Pro-actively remove mapping of old generations from the cache. I will do this
in a follow up commit.
* Reduce the memory foot print of the keys (stable ids of node states) of the
cache. See OAK-4797.
Beyond this we could try coming up with a more memory efficient way to
structure the cache. As Java doesn't have memory efficient structs, we suffer
quite a bit of memory overhead from extra instances per mapping (keys and
entries). However, I'm a bit reluctant to invest here as effort, complexity and
risk would be quite high an would block progress in other areas. In the end the
extra memory spent here is a trade-off of our technology choice.
was (Author: mduerig):
To address the OOME issue we have seen while evaluating this approach with the
OAK-4635-6 branch I suggest to
* Pro-actively remove mapping of old generations from the cache. I will do this
in a follow up commit.
* Reduce the memory foot print of the keys (stable ids of node states) of the
cache. See 4797.
Beyond this we could try coming up with a more memory efficient way to
structure the cache. As Java doesn't have memory efficient structs, we suffer
quite a bit of memory overhead from extra instances per mapping (keys and
entries). However, I'm a bit reluctant to invest here as effort, complexity and
risk would be quite high an would block progress in other areas. In the end the
extra memory spent here is a trade-off of our technology choice.
> Improve cache eviction policy of the node deduplication cache
> -------------------------------------------------------------
>
> Key: OAK-4635
> URL: https://issues.apache.org/jira/browse/OAK-4635
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: segment-tar
> Reporter: Michael Dürig
> Assignee: Michael Dürig
> Labels: perfomance
> Fix For: Segment Tar 0.0.12
>
> Attachments: OAK-4635.m, OAK-4635.pdf
>
>
> {{NodeCache}} uses one stripe per depth (of the nodes in the tree). Once its
> overall capacity (default 1000000 nodes) is exceeded, it clears all nodes
> from the stripe with the greatest depth. This can be problematic when the
> stripe with the greatest depth contains most of the nodes as clearing it
> would result in an almost empty cache.
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