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https://github.com/NixOS/nixpkgs.git
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c66b12ff90
This optimizes the performance of the hook on machines with multiple cores. The previous implementation was slow, as it was launching two extra processes per symlink (readlink and ln) while not making use of multiprocessing. The following improvements were made: - don't even execute the hook if dontRewriteSymlinks is set - replace multiple find calls with single find call over all outputs - use xargs -P to process symlinks in parallel - add test to check that the hook operates as expected
36 lines
1.0 KiB
Bash
36 lines
1.0 KiB
Bash
# symlinks are often created in postFixup
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# don't use fixupOutputHooks, it is before postFixup
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if [[ -z "${dontRewriteSymlinks-}" ]]; then
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postFixupHooks+=(_makeSymlinksRelative)
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fi
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# For every symlink in $output that refers to another file in $output
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# ensure that the symlink is relative.
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# This increases the chance that NAR files can be deduplicated.
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_makeSymlinksRelative() {
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local prefixes
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prefixes=()
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for output in $(getAllOutputNames); do
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[ ! -e "${!output}" ] && continue
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prefixes+=( "${!output}" )
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done
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find "${prefixes[@]}" -type l -printf '%H\0%p\0' \
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| xargs -0 -n2 -r -P "$NIX_BUILD_CORES" sh -c '
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output="$1"
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link="$2"
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linkTarget=$(readlink "$link")
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# only touch links that point inside the same output tree
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[[ $linkTarget == "$output"/* ]] || exit 0
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if [ ! -e "$linkTarget" ]; then
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echo "the symlink $link is broken, it points to $linkTarget (which is missing)"
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fi
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echo "making symlink relative: $link"
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ln -snrf "$linkTarget" "$link"
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' _
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}
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