On Wed 13-04-11 16:59:41, Wu Fengguang wrote: > 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> Well, I have nothing against this change as such but what I don't like is that it just changes magical +2 for similarly magical +0. It's clear that this will lead to more rapid updates of proportions of bdi's share of writeback and thread's share of dirtying but why +0? Why not +1 or -1? So I'd prefer to get some understanding of why do we need to update the proportion period and why 4-times faster is just the right amount of faster :) If I remember right you had some numbers for this, didn't you? Honza > --- > 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); > } > > /* > > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
