On Mon, 2014-06-09 at 21:27 +0800, Chen Yucong wrote: > Via https://lkml.org/lkml/2013/4/10/334 , we can find that recording the > original scan targets introduces extra 40 bytes on the stack. This patch > is able to avoid this situation and the call to memcpy(). At the same time, > it does not change the relative design idea. > > ratio = original_nr_file / original_nr_anon; > > If (nr_file > nr_anon), then ratio = (nr_file - x) / nr_anon. > x = nr_file - ratio * nr_anon; > > if (nr_file <= nr_anon), then ratio = nr_file / (nr_anon - x). > x = nr_anon - nr_file / ratio; > Hi Andrew Morton, I think the patch [PATCH] mm-vmscanc-avoid-recording-the-original-scan-targets-in-shrink_lruvec-fix.patch which I committed should be discarded. Because It have some critical defects. 1) If we want to solve the divide-by-zero and unfair problems, it needs to two variables for recording the ratios. 2) For "x = nr_file - ratio * nr_anon", the "x" is likely to be a negative number. we can assume: nr[LRU_ACTIVE_FILE] = 30 nr[LRU_INACTIVE_FILE] = 30 nr[LRU_ACTIVE_ANON] = 0 nr[LRU_INACTIVE_ANON] = 40 ratio = 60/40 = 3/2 When the value of (nr_reclaimed < nr_to_reclaim) become false, there are the following results: nr[LRU_ACTIVE_FILE] = 15 nr[LRU_INACTIVE_FILE] = 15 nr[LRU_ACTIVE_ANON] = 0 nr[LRU_INACTIVE_ANON] = 25 nr_file = 30 nr_anon = 25 x = 30 - 25 * (3/2) = 30 - 37.5 = -7.5. The result is too terrible. 3) This method is less accurate than the original, especially for the qualitative difference between FILE and ANON that is very small. thx! cyc -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>