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Commit efab0b5d authored by Andres Salomon's avatar Andres Salomon Committed by David Woodhouse
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[JFFS2] force the jffs2 GC daemon to behave a bit better 



I've noticed some pretty poor behavior on OLPC machines after bootup, when
gdm/X are starting.  The GCD monopolizes the scheduler (which in turns
means it gets to do more nand i/o), which results in processes taking much
much longer than they should to start.

As an example, on an OLPC machine going from OFW to a usable X (via
auto-login gdm) takes 2m 30s.  The majority of this time is consumed by
the switch into graphical mode.  With this patch, we cut a full 60s off of
bootup time.  After bootup, things are much snappier as well.

Note that we have seen a CRC node error with this patch that causes the machine
to fail to boot, but we've also seen that problem without this patch.

Signed-off-by: default avatarAndres Salomon <dilinger@debian.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent ab00d682

fs/jffs2/background.c

+11 −7
Original line number Diff line number Diff line
@@ -95,13 +95,17 @@ static int jffs2_garbage_collect_thread(void *_c) 
			spin_unlock(&c->erase_completion_lock);

			



		/* 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();

		/* Problem - immediately after bootup, the GCD spends a lot

		 * of time in places like jffs2_kill_fragtree(); so much so

		 * that userspace processes (like gdm and X) are starved

		 * despite plenty of cond_resched()s and renicing.  Yield()

		 * doesn't help, either (presumably because userspace and GCD

		 * are generally competing for a higher latency resource -

		 * disk).

		 * This forces the GCD to slow the hell down.   Pulling an

		 * inode in with read_inode() is much preferable to having

		 * the GC thread get there first. */

		schedule_timeout_interruptible(msecs_to_jiffies(50));



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

		 */