[PATCH v2] tags: much faster, parallel "make tags"

[Alexey Dobriyan <adobriyan@gmail.com>]

On Wed, Apr 15, 2015 at 03:24:26PM +0200, 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.
> 
> 
> > +
> > +	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.

If "-a" is omitted, tags file becomes broken for some reason,
e. g. "file_operations" isn't there anymore.

> > +	# 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.

I don't understand why would you fake etags with ctags.
It would go via "emacs" path, which is not changed.
----------------------------------------------------------------------
[PATCH] tags: much faster, parallel "make tags"

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 |   36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -152,7 +152,19 @@ dogtags()
 
 exuberant()
 {
-	all_target_sources | xargs $1 -a                        \
+	rm -f .make-tags.*
+
+	all_target_sources >.make-tags.src
+	NR_CPUS=$(getconf _NPROCESSORS_ONLN 2>/dev/null || echo 1)
+	NR_LINES=$(wc -l <.make-tags.src)
+	NR_LINES=$((($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 $i | sed -e 's/.*\.//')
+		# -u: don't sort now, sort later
+		xargs <$i $1 -a -f .make-tags.$N -u		\
 	-I __initdata,__exitdata,__initconst,			\
 	-I __cpuinitdata,__initdata_memblock			\
 	-I __refdata,__attribute,__maybe_unused,__always_unused \
@@ -211,7 +223,21 @@ exuberant()
 	--regex-c='/DEFINE_PCI_DEVICE_TABLE\((\w*)/\1/v/'		\
 	--regex-c='/(^\s)OFFSET\((\w*)/\2/v/'				\
 	--regex-c='/(^\s)DEFINE\((\w*)/\2/v/'				\
-	--regex-c='/DEFINE_HASHTABLE\((\w*)/\1/v/'
+	--regex-c='/DEFINE_HASHTABLE\((\w*)/\1/v/'			\
+	&
+	done
+	wait
+	rm -f .make-tags.src .make-tags.src.*
+
+	# write header
+	$1 -f $2 /dev/null
+	# remove headers
+	for i in .make-tags.*; do
+		sed -i -e '/^!/d' $i &
+	done
+	wait
+	sort .make-tags.* >>$2
+	rm -f .make-tags.*
 
 	all_kconfigs | xargs $1 -a                              \
 	--langdef=kconfig --language-force=kconfig              \
@@ -276,7 +302,7 @@ emacs()
 xtags()
 {
 	if $1 --version 2>&1 | grep -iq exuberant; then
-		exuberant $1
+		exuberant $1 $2
 	elif $1 --version 2>&1 | grep -iq emacs; then
 		emacs $1
 	else
@@ -322,13 +348,13 @@ case "$1" in
 
 	"tags")
 		rm -f tags
-		xtags ctags
+		xtags ctags tags
 		remove_structs=y
 		;;
 
 	"TAGS")
 		rm -f TAGS
-		xtags etags
+		xtags etags TAGS
 		remove_structs=y
 		;;
 esac