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From Jukka Zitting <jukka.zitt...@gmail.com>
Subject Re: java.util.UUID
Date Thu, 24 Oct 2013 13:38:06 GMT

On Thu, Oct 24, 2013 at 2:48 AM, Tobias Bocanegra <tripod@apache.org> wrote:
> [Inline image 1]

The image didn't survive it's trip to the mailing list. Can you post a
link to it?

> I thought that Oak does not use UUIDs so much anymore - why do I have 20mb of them? they
are all allocated via the SegmentMK.

The SegmentMK uses UUIDs to identify segments.

Currently multiple copies of each UUID are kept in memory, one for the
segment itself and another for each other segment that contains a
reference to it. Avoiding those duplicates should bring the memory
requirement down by an order of magnitude.

Another reason for the high memory use is that currently the TarMK
(not the MongoDB backend of SegmentMK) keeps all Segment UUIDs in
memory all the time to avoid having to scan through the tar files when
looking up a segment. A segment index at the end of each tar file
should take care of that.


Jukka Zitting

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