[PATCH] initscripts: populate-volatiles: Speed up processing

[Joshua Watt <jpewhacker@gmail.com>]

Checking the requirements for each volatiles file in the
populate-volatiles script can be very slow when there are a large number
of volatiles files, easily consuming over 80% of the processing time.
These checks don't usually uncover any problems so concatenate all the
volatiles files together and process them as one large file for a "fast
path" option. This ensures that the penalty for checking the
requirements is only incurred once. In the event that checking the
requirements for the unified file fails, fall back to the slow process
of checking each one individually so that the offending one can be
skipped.

[YOCTO #12949]

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
---
 .../initscripts-1.0/populate-volatile.sh      | 31 +++++++++++++++++--
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/meta/recipes-core/initscripts/initscripts-1.0/populate-volatile.sh b/meta/recipes-core/initscripts/initscripts-1.0/populate-volatile.sh
index 35316ec2baa..51eef0ca713 100755
--- a/meta/recipes-core/initscripts/initscripts-1.0/populate-volatile.sh
+++ b/meta/recipes-core/initscripts/initscripts-1.0/populate-volatile.sh
@@ -154,8 +154,11 @@ check_requirements() {
 
 apply_cfgfile() {
 	CFGFILE="$1"
+	SKIP_REQUIREMENTS="$2"
 
-	check_requirements "${CFGFILE}" || {
+	[ "${VERBOSE}" != "no" ] && echo "Applying ${CFGFILE}"
+
+	[ "${SKIP_REQUIREMENTS}" == "yes" ] || check_requirements "${CFGFILE}" || {
 		echo "Skipping ${CFGFILE}"
 		return 1
 	}
@@ -231,10 +234,32 @@ then
 	sh ${ROOT_DIR}/etc/volatile.cache
 else
 	rm -f ${ROOT_DIR}/etc/volatile.cache ${ROOT_DIR}/etc/volatile.cache.build
-	for file in `ls -1 "${CFGDIR}" | sort`; do
-		apply_cfgfile "${CFGDIR}/${file}"
+
+	# Fast path: check_requirements is slow and most of the time doesn't
+	# find any problems. If there are a lot of config files, it is much
+	# faster to to concatenate them all together and process them once to
+	# avoid the overhead of calling check_requirements repeatedly
+	TMP_FILE="${TMPROOT}/tmp_volatile.$$"
+	rm -f "$TMP_FILE"
+
+	CFGFILES="`ls -1 "${CFGDIR}" | sort`"
+	for file in ${CFGFILES}; do
+		cat "${CFGDIR}/${file}" >> "$TMP_FILE"
 	done
 
+	if check_requirements "$TMP_FILE"
+	then
+		apply_cfgfile "$TMP_FILE" "yes"
+	else
+		# Slow path: One or more config files failed requirements.
+		# Process each one individually so the offending one can be
+		# skipped
+		for file in ${CFGFILES}; do
+			apply_cfgfile "${CFGDIR}/${file}"
+		done
+	fi
+	rm "$TMP_FILE"
+
 	[ -e ${ROOT_DIR}/etc/volatile.cache.build ] && sync && mv ${ROOT_DIR}/etc/volatile.cache.build ${ROOT_DIR}/etc/volatile.cache
 fi
 
-- 
2.17.1