GenChangeLogs: parallelize remaining git calls, scale linearly (bug 565540)

Move all git calls to the subprocesses, so performance scales linearly
with --jobs.

X-Gentoo-Bug: 565540
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=565540
Acked-by: Alexander Berntsen <bernalex@gentoo.org>

1 files changed, 18 insertions, 15 deletions

diff --git a/bin/egencache b/bin/egencache
index b44ad11b6..1cc2f3d4f 100755
--- a/bin/egencache
+++ b/bin/egencache
@@ -781,6 +781,23 @@ class GenChangeLogs(object):
 				encoding=_encodings['stdio'], errors='strict')
 
 	def generate_changelog(self, cp):
+
+		os.chdir(os.path.join(self._repo_path, cp))
+		# Determine whether ChangeLog is up-to-date by comparing
+		# the newest commit timestamp with the ChangeLog timestamp.
+		lmod = self.grab(['git', self._work_tree, 'log', '--format=%ct', '-1', '.'])
+		if not lmod:
+			# This cp has not been added to the repo.
+			return
+
+		try:
+			cmod = os.stat('ChangeLog').st_mtime
+		except OSError:
+			cmod = 0
+
+		if float(cmod) >= float(lmod):
+			return
+
 		try:
 			output = io.open(self._changelog_output,
 				mode='w', encoding=_encodings['repo.content'],
@@ -913,21 +930,7 @@ class GenChangeLogs(object):
 			return
 
 		for cp in self._portdb.cp_all():
-			os.chdir(os.path.join(self._repo_path, cp))
-			# Determine whether ChangeLog is up-to-date by comparing
-			# the newest commit timestamp with the ChangeLog timestamp.
-			lmod = self.grab(['git', self._work_tree, 'log', '--format=%ct', '-1', '.'])
-			if not lmod:
-				# This cp has not been added to the repo.
-				continue
-
-			try:
-				cmod = os.stat('ChangeLog').st_mtime
-			except OSError:
-				cmod = 0
-
-			if float(cmod) < float(lmod):
-				yield AsyncFunction(target=self.generate_changelog, args=[cp])
+			yield AsyncFunction(target=self.generate_changelog, args=[cp])
 
 	def run(self):
 		return run_main_scheduler(