On Wed, Dec 1, 2010 at 12:08 PM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > T0: Task1 wakeup_kswapd(order=3) > T1: kswapd enters balance_pgdat > T2: Task2 wakeup_kswapd(order=2), because pages reclaimed by kswapd are used > quickly > T3: kswapd exits balance_pgdat. kswapd will do check. Now new order=2, > pgdat->kswapd_max_order will become 0, but order=3, if sleeping_prematurely, > then order will become pgdat->kswapd_max_order(0), while at this time the > order should 2 > This isn't a big deal, but we do have a small window the order is wrong. > > Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxx> But you need the description more easily. I try it. T0 : Task 1 wakes up kswapd with order-3 T1 : So, kswapd starts to reclaim pages using balance_pgdat T2: Task 2 wakes up kswapd with order-2 because pages reclaimed by T1 are consumed quickly. T3: kswapd exits balance_pgdat and will recheck remained work T4-1 : In beginning of kswapd's loop, pgdat->kswapd_max_order will be reset with zero. T4-2: If previous balance_pgdat can't meet requirement of order-3 free pages by high watermark, it can start reclaiming again. T4-3 :Unfortunately, balance_pgdat's argument _order_ is pgdat->kswapd_max_order which was zero. It should have been 2. Regardless of my suggestion, I will add my Reviewed-by. > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index d31d7ce..15cd0d2 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2450,7 +2450,7 @@ static int kswapd(void *p) > } > } > > - order = pgdat->kswapd_max_order; > + order = max_t(unsigned long, new_order, pgdat->kswapd_max_order); > } > finish_wait(&pgdat->kswapd_wait, &wait); > > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxxx For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href