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SubjectRe: [PATCH] tags: much faster, parallel "make tags"
On 2015-04-15 15:24, Michal Marek wrote:
> 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.

I meant, leave the concept as is, but fix the detection of the number of
cpus.


>> + # 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.

Additionally, the TAGS file must not be sorted.

Michal


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