massive v6 add speed/memory improvement
v6 add: Take advantage of improved SIGPIPE handler in git 2.5 to speed up the clean filter by not reading the file content from the pipe. This also avoids git buffering the whole file content in memory. When built with an older git, still consumes stdin. If built with a newer git and used with an older one, it breaks, but that's acceptable -- checking the git version every time would make repeated smudge runs slow. This commit was supported by the NSF-funded DataLad project.
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@ -65,16 +65,16 @@ git-annex should use smudge/clean filters.
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* When git runs the smudge filter, it buffers all its output in ram before
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writing it to a file. So, checking out a branch with a large v6 unlocked files
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can cause git to use a lot of memory.
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(This needs to be fixed in git, but my proposed interface in
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This needs to be fixed in git, but my proposed interface in
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<http://thread.gmane.org/gmane.comp.version-control.git/294425> would
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avoid the problem for git checkout, since it would use the new interface
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and not the smudge filter.)
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and not the smudge filter.
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* When `git add` is run with a large file, it allocates memory for
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the whole file content, even though it's only going
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to stream it to the clean filter. My proposed smudge/clean
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interface patch also fixed this problem, since it made git not read
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the file at all.
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Last verified with git 2.18 in 2018.
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To check: Does the long-running filter process interface have the same
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problem?
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* Eventually (but not yet), make v6 the default for new repositories.
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Note that the assistant forces repos into direct mode; that will need to
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@ -0,0 +1,11 @@
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[[!comment format=mdwn
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username="joey"
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subject="""re: Git 2.5 allows smudge filters to not read all of stdin"""
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date="2018-08-09T22:11:00Z"
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content="""
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@torarnv thanks for pointing that out.. I finally got around to verifying
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that, and was able to speed up the smudge filter. Also this avoids the
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problem that git for some reason buffers the whole file content in memory
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when it sends it to the smudge filter, which is a pretty bad memory leak in git
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that no longer affects this.
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"""]]
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