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SubjectRe: [PATCH] tags: much faster, parallel "make tags"
On 2015-04-14 19:20, Alexey Dobriyan wrote:
> ctags is single-threaded program. Split list of files to be tagged into
> equal parts, 1 part for each CPU and then merge the results.
>
> Speedup on one 2-way box I have is ~143 s => ~99 s (-31%).
> On another 4-way box: ~120 s => ~65 s (-46%!).
>
> Resulting "tags" files aren't byte-for-byte identical because ctags
> program numbers anon struct and enum declarations with "__anonNNN"
> symbols. If those lines are removed, "tags" file becomes byte-for-byte
> identical with those generated with current code.
>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>
> scripts/tags.sh | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> --- a/scripts/tags.sh
> +++ b/scripts/tags.sh
> @@ -152,7 +152,24 @@ dogtags()
>
> exuberant()
> {
> - all_target_sources | xargs $1 -a \
> + NR_CPUS=1
> + if [ -e /proc/cpuinfo ]; then
> + NR_CPUS=$(grep -e '^processor : ' /proc/cpuinfo | wc -l)
> + fi

I wonder if we should rather respect the -j option to make here. But
then most people probably won't realize that make tags is parallel and
will not use -j when generating tags. So let's leave it as is.


> +
> + rm -f .make-tags.src.* .make-tags.*

.make-tags.src.* is a subset of .make-tags.*


> +
> + all_target_sources >.make-tags.src
> + # seems like Useless Use of cat(1) but not really
> + NR_LINES=$(cat .make-tags.src | wc -l)
> + NR_LINES=$((($NR_LINES + $NR_CPUS - 1) / $NR_CPUS))
> +
> + split -a 6 -d -l $NR_LINES .make-tags.src .make-tags.src.
> +
> + for i in .make-tags.src.*; do
> + N=$(echo $i | sed -e 's/.*\.//')
> + # -u: don't sort now, sort later
> + cat $i | xargs $1 -a -f .make-tags.$N -u \

xargs <$i $1 ... if you are concerned about uses of cat(1) ;) and the -a
option is not necessary since we are creating the tmp files.


> + # write header
> + $1 -f tags /dev/null
> + # remove header
> + for i in .make-tags.*; do
> + sed -i -e '/^!/d' $i
> + done
> + sort .make-tags.* >>tags

The hardcoded "tags" filename will break 'make TAGS' when using
exuberant ctags via an 'etags' symlink.

Michal


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