Commit f8a922c7 authored Mar 08, 2007 by David Woodhouse

[JFFS2] Use yield() between GC passes in background thread.



The garbage collection thread is strictly an optimisation. Everything it
does would also be done just-in-time in the context of something in
userspace trying to access the file system.

Sometimes, however, it's a pessimisation. Especially during early boot
when it's checksumming nodes and scanning inodes which are shortly going
to be pulled in by read_inode anyway. We end up building the rbtree of
node coverage twice for the same inode.

By switching to yield() instead of cond_resched() in the main loop, we
observe boot times on the OLPC system going down from about 100 seconds to
60.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

parent 89e2bf61

fs/jffs2/background.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -99,7 +99,13 @@ static int jffs2_garbage_collect_thread(void *_c)
		if (try_to_freeze())
		continue;

		cond_resched();
		/* This thread is purely an optimisation. But if it runs when
		other things could be running, it actually makes things a
		lot worse. Use yield() and put it at the back of the runqueue
		every time. Especially during boot, pulling an inode in
		with read_inode() is much preferable to having the GC thread
		get there first. */
		yield();

		/* Put_super will send a SIGKILL and then wait on the sem.
		*/