From: David Woodhouse Date: Thu, 8 Mar 2007 10:28:30 +0000 (+0000) Subject: [JFFS2] Use yield() between GC passes in background thread. X-Git-Tag: v2.6.21-rc4~69^2~8 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8a922c7bb4d93bd84b7371a8e2571e667d2afb5;p=linux-2.6 [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 --- diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c index 6eb3daebd5..888f236e54 100644 --- a/fs/jffs2/background.c +++ b/fs/jffs2/background.c @@ -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. */