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https://issues.apache.org/jira/browse/SVN-4667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15795158#comment-15795158
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Julian Foad commented on SVN-4667:
----------------------------------
Attached "repro-test-2.patch", a patch which adds the reproduction recipe I'm
using so far, in the form of a test case. It generates a repository with N=300
(for example) branches, each with a unique file changed, and merged to trunk
such that trunk gets N files with subtree mergeinfo, each referring to up to N
branches (half of N, on average).
I can then run test merges, with debugging prints in them, to view the memory
increase:
{code:none}
# this runs a merge from trunk to branch,
# with WC directory 'A' switched to a branch:
$ (cd
obj-dir/subversion/tests/cmdline/svn-test-work/working_copies/mergeinfo_tests-14/
&& \
svn revert -q -R A/ && \
svn merge -q ^/A A)
DBG: merge.c:12587: using 8+3 MB; increase +2 MB
DBG: merge.c:12418: using 8+25 MB; increase +21 MB
DBG: merge.c:12455: using 8+34 MB; increase +9 MB
DBG: merge.c:9378: using 8+37 MB; increase +3 MB
DBG: merge.c:9378: using 8+43 MB; increase +6 MB
{code}
I don't know how representative this repro-test is of the customer's use case,
but it provides a starting point.
> Merge uses large amount of memory
> ---------------------------------
>
> Key: SVN-4667
> URL: https://issues.apache.org/jira/browse/SVN-4667
> Project: Subversion
> Issue Type: Bug
> Affects Versions: 1.9.4
> Reporter: Julian Foad
> Attachments: repro-test-1.patch, repro-test-2.patch
>
>
> A WANdisco customer found that a merge will not complete with 4 GB RAM and
> will complete with 5 GB RAM available.
> The branches involved have subtree mergeinfo on over 3500 files, each
> referring to about 350 branches on average, and just over 1 revision range on
> average per mergeinfo line. Average path length is under 100 bytes.
> This seems already far too much memory usage for the size of the data set,
> and the size of the data set is growing.
> This issue is about reducing the amount of RAM Subversion uses given this
> data set. Another way to approach the problem is to reduce the amount of
> subtree mergeinfo by changing the work flow practices; that approach is also
> being investigated but is not in the scope of this issue, except to note that
> the tools "svn-mergeinfo-normalizer" and "svn-clean-mergeinfo.pl" both also
> fail to execute in the available RAM.
> (WANdisco's internal issue id: SVNB-1952.)
> (For reference, past issues about merge using too much memory include
> SVN-3393 "Merge consuming too much memory" and SVN-3854 "Out of memory during
> merge with many Tree Conflicts".)
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