[PATCH 4/4] writeback: reduce per-bdi dirty threshold ramp up time

[Wu Fengguang]

Reduce the dampening for the control system, yielding faster
convergence. The change is a bit conservative, as smaller values may
lead to noticeable bdi threshold fluctuates in low memory JBOD setup.

CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
CC: Richard Kennedy <richard@xxxxxxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 mm/page-writeback.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next.orig/mm/page-writeback.c	2011-03-02 14:52:19.000000000 +0800
+++ linux-next/mm/page-writeback.c	2011-03-02 15:00:17.000000000 +0800
@@ -145,7 +145,7 @@ static int calc_period_shift(void)
 	else
 		dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
 				100;
-	return 2 + ilog2(dirty_total - 1);
+	return ilog2(dirty_total - 1);
 }
 
 /*


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