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perf(dracut-functions): optimize _inst_rule_programs() #2352

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perf(dracut-functions): optimize _inst_rule_programs() #2352

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23 changes: 20 additions & 3 deletions dracut-functions.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -1202,6 +1202,12 @@ dracut_need_initqueue() {
# attempt to install any programs specified in a udev rule
_inst_rule_programs() {
local _prog _bin
local -A _rule_bins=()

# cache installed rule programs
if ! declare -p _rule_programs_cache 2> /dev/null | grep -q "declare -A"; then
declare -gxA _rule_programs_cache=()

@bdrung bdrung Apr 9, 2026

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I am +1 for calling inst_multiple once, I am not sure about the added cache.

How much difference does this cache make? Could we do the caching in inst_multiple instead? I would go one step further for #1419: Add staging functions similar to the inst_* functions. These functions would just collect what should be added. Then call an dracut-intsall equivalent to only write a manifest for 3cpio.

@aafeijoo-suse aafeijoo-suse Apr 10, 2026

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I am +1 for calling inst_multiple once, I am not sure about the added cache.

How much difference does this cache make?

I don't think hyperfine can show a real improvement with these kinds of minor performance patches. That depends on multiple factors. But IMO it seems like a logical and small code improvement. I remember when I implemented 80f2caf, I didn't see anything important with hyperfine, but that turned out to be critical in some systems (https://bugzilla.redhat.com/show_bug.cgi?id=2278534#c8).

Could we do the caching in inst_multiple instead? I would go one step further for #1419: Add staging functions similar to the inst_* functions. These functions would just collect what should be added. Then call an dracut-intsall equivalent to only write a manifest for 3cpio.

This is a simple, localized performance improvement. I know you would like to improve how the inst* functions work, but that would be another story. You would need to track the name of the module and all the specific options passed to dracut-install for each call, to be able to say "this module cannot be installed because...".

@bdrung bdrung Apr 10, 2026

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We had very slow dracut-install executions on some ARM systems. So reducing the amount of calls we do to dracut-install helped there. That difference could be measured by hyperfine back then. So maybe I should do my benchmarks on a Raspberry Pi instead. I did the hyperfine benchmark to see if we should include this patch in the upcoming Ubuntu 26.04.

fi

# shellcheck disable=SC2013
for _prog in $(sed -nr 's/.*PROGRAM==?"([^ "]+).*/\1/p' "$1"); do
Expand All @@ -1215,7 +1221,10 @@ _inst_rule_programs() {
}
fi

[[ $_bin ]] && inst_binary "$_bin"
if [[ $_bin ]] && [[ ${_rule_bins[$_bin]:-} != 1 ]] && [[ ${_rule_programs_cache[$_bin]:-} != 1 ]]; then
_rule_bins[$_bin]=1
_rule_programs_cache[$_bin]=1
fi
done

# shellcheck disable=SC2013
Expand All @@ -1230,7 +1239,10 @@ _inst_rule_programs() {
}
fi

[[ $_bin ]] && inst_binary "$_bin"
if [[ $_bin ]] && [[ ${_rule_bins[$_bin]:-} != 1 ]] && [[ ${_rule_programs_cache[$_bin]:-} != 1 ]]; then
_rule_bins[$_bin]=1
_rule_programs_cache[$_bin]=1
fi
done

# shellcheck disable=SC2013
Expand All @@ -1245,8 +1257,13 @@ _inst_rule_programs() {
}
fi

[[ $_bin ]] && inst_multiple "$_bin"
if [[ $_bin ]] && [[ ${_rule_bins[$_bin]:-} != 1 ]] && [[ ${_rule_programs_cache[$_bin]:-} != 1 ]]; then
_rule_bins[$_bin]=1
_rule_programs_cache[$_bin]=1
fi
done

((${#_rule_bins[@]} > 0)) && inst_multiple "${!_rule_bins[@]}"
}

# attempt to create any groups and users specified in a udev rule
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