From mboxrd@z Thu Jan 1 00:00:00 1970 Message-Id: <20080129154947.110268504@szeredi.hu> References: <20080129154900.145303789@szeredi.hu> Date: Tue, 29 Jan 2008 16:49:01 +0100 From: Miklos Szeredi Subject: [patch 1/6] mm: bdi: tweak task dirty penalty Content-Disposition: inline; filename=bdi-task-dirty.patch Sender: owner-linux-mm@kvack.org From: Peter Zijlstra Return-Path: To: akpm@linux-foundation.org Cc: a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org List-ID: 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 Signed-off-by: Miklos Szeredi --- 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; -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org