Commit f8a922c7 authored by David Woodhouse's avatar 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: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent 89e2bf61
......@@ -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.
*/
......
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