Messages in this thread Patch in this message | | | Date | Tue, 29 Jan 2008 16:49:01 +0100 | From | Miklos Szeredi <> | Subject | [patch 1/6] mm: bdi: tweak task dirty penalty |
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Penalizing heavy dirtiers with 1/8-th the total dirty limit might be rather excessive on large memory machines. Use sqrt to scale it sub-linearly.
Update the comment while we're there.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> ---
Index: linux/mm/page-writeback.c =================================================================== --- linux.orig/mm/page-writeback.c 2008-01-17 19:00:56.000000000 +0100 +++ linux/mm/page-writeback.c 2008-01-18 13:07:16.000000000 +0100 @@ -219,17 +219,21 @@ static inline void task_dirties_fraction } /* - * scale the dirty limit + * Task specific dirty limit: * - * task specific dirty limit: + * dirty -= 8 * sqrt(dirty) * p_{t} * - * dirty -= (dirty/8) * p_{t} + * Penalize tasks that dirty a lot of pages by lowering their dirty limit. This + * avoids infrequent dirtiers from getting stuck in this other guys dirty + * pages. + * + * Use a sub-linear function to scale the penalty, we only need a little room. */ static void task_dirty_limit(struct task_struct *tsk, long *pdirty) { long numerator, denominator; long dirty = *pdirty; - u64 inv = dirty >> 3; + u64 inv = 8*int_sqrt(dirty); task_dirties_fraction(tsk, &numerator, &denominator); inv *= numerator; --
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