On Tue, 2014-06-10 at 16:33 -0700, Andrew Morton wrote: > On Mon, 9 Jun 2014 21:27:16 +0800 Chen Yucong <slaoub@xxxxxxxxx> 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; > > > > ... > > > > Are you sure this is an equivalent-to-before change? If so, then I > can't immediately see why :( > The relative design idea is to keep ratio == scan_target[anon] : scan_target[file] == really_scanned_num[anon] : really_scanned_num[file] The original implementation is ratio == (scan_target[anon] * percentage_anon) / (scan_target[file] * percentage_file) To keep the original ratio, percentage_anon should equal to percentage_file. In other word, we need to calculate the difference value between percentage_anon and percentage_file, we also have to record the original scan targets for this. Instead, we can calculate the *ratio* at the beginning of shrink_lruvec(). As a result, this can avoid introducing the extra 40 bytes. In short, we have the same goal: keep the same *ratio* from beginning to end. 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>