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[[!comment format=mdwn
username="joey"
subject="""comment 1"""
date="2016-07-06T15:59:34Z"
content="""
Startup time is also particulary important when git-annex is being used as
a smudge/clean filter in v6 mode, since it's run once per file git operates
on.
---
What I'd look at before prelinking is, does your git-annex executable
dynamically link haskell libraries?
That was the case for a while in the standalone builds, until I noticed it
caused too much linker time and put it back to static linking of the
haskell libs. Leaving only 34 or so C shared libs.
---
Did some preliminary benchmarking here of `git-annex version --raw`
* deb package build: 0.04 seconds min
* deb package build prelinked: ~0.03 seconds min
* standalone build: 0.05 seconds min
* git-annex modified to print "hi" and exit immediately: 0.02 seconds min
So, the overhead of the wrapper scripts for the standalone build is around
0.01 seconds.
And, prelinking does help a little bit (although probably closer to 0.005
seconds than 0.01; my measurements are too coarse to get a good number).
Meanwhile, 0.02 seconds are used after git-annex starts up. This overhead
includes finding the path to the git repository, running and parsing `git
config --list`, etc.
But what about that 0.02 seconds just to print "hi"...?
----
With strace I noticed a very interesting thing. Despite being statically
linked against the haskell libraries, the linker searches in all their
paths for all C libraries. This adds around 30000 failed open() calls
to git-annex's startup. This is done even after prelinking. It must be a
significant part of the startup time.
Filed a bug: <https://github.com/haskell/cabal/issues/3524>
Put in a chrpath workaround, but only when git-annex is built with "make"
(not cabal install git-annex).
Updated benchmarks:
* deb package build: 0.02 seconds min
* deb package build prelinked: ~0.02 seconds min
* standalone build: 0.03 seconds min
* git-annex modified to print "hi" and exit immediately: 0.01 seconds min
"""]]
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