On Thu, Feb 16, 2017 at 02:23:08PM +0800, Hillf Danton wrote:
> On February 15, 2017 5:23 PM Mel Gorman wrote:
> > */
> > static int kswapd(void *p)
> > {
> > - unsigned int alloc_order, reclaim_order, classzone_idx;
> > + unsigned int alloc_order, reclaim_order;
> > + unsigned int classzone_idx = MAX_NR_ZONES - 1;
> > pg_data_t *pgdat = (pg_data_t*)p;
> > struct task_struct *tsk = current;
> >
> > @@ -3447,20 +3466,23 @@ static int kswapd(void *p)
> > tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> > set_freezable();
> >
> > - pgdat->kswapd_order = alloc_order = reclaim_order = 0;
> > - pgdat->kswapd_classzone_idx = classzone_idx = 0;
> > + pgdat->kswapd_order = 0;
> > + pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
> > for ( ; ; ) {
> > bool ret;
> >
> > + alloc_order = reclaim_order = pgdat->kswapd_order;
> > + classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
> > +
> > kswapd_try_sleep:
> > kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
> > classzone_idx);
> >
> > /* Read the new order and classzone_idx */
> > alloc_order = reclaim_order = pgdat->kswapd_order;
> > - classzone_idx = pgdat->kswapd_classzone_idx;
> > + classzone_idx = kswapd_classzone_idx(pgdat, 0);
> > pgdat->kswapd_order = 0;
> > - pgdat->kswapd_classzone_idx = 0;
> > + pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
> >
> > ret = try_to_freeze();
> > if (kthread_should_stop())
> > @@ -3486,9 +3508,6 @@ static int kswapd(void *p)
> > reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
> > if (reclaim_order < alloc_order)
> > goto kswapd_try_sleep;
>
> If we fail order-5 request, can we then give up order-5, and
> try order-3 if requested, after napping?
>
That has no bearing upon this patch. At this point, kswapd has stopped
reclaiming at the requested order and is preparing to sleep. If there is
a parallel request for order-3 while it's sleeping, it'll wake and start
reclaiming at order-3 as requested.
--
Mel Gorman
SUSE Labs
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