jffs2: force the jffs2 GC daemon to behave a bit better
PATCH 6/6 jffs2: force the jffs2 GC daemon to behave a bit better
From: Andres Salomon <[email protected]>
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.
---
fs/jffs2/background.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
fs/jffs2/background.c renamed from fs/jffs2/background.c~jffs2-force-the-jffs2-gc-daemon-to-behave-a-bit-better +11 -7
@@ -95,13 +95,17 @@ static int jffs2_garbage_collect_thread(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. */
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