> Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote: > > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote: > > > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote: > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone > > > *preferred_zone, > > > struct list_head *list; > > > bool cold = ((gfp_flags & __GFP_COLD) != 0); > > > struct page *page; > > > - unsigned long flags; > > > > > > - local_irq_save(flags); > > > + preempt_disable(); > > > pcp = &this_cpu_ptr(zone->pageset)->pcp; > > > list = &pcp->lists[migratetype]; > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype, > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone > > > *preferred_zone, > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); > > > zone_statistics(preferred_zone, zone, gfp_flags); > > > } > > > - local_irq_restore(flags); > > > + preempt_enable(); > > > return page; > > > } > > > > > With PREEMPT configured, preempt_enable() adds entry point to schedule(). > > Is that needed when we try to allocate a page? > > > > Not necessarily but what are you proposing as an alternative?
preempt_enable_no_resched() looks at first glance a choice for us to avoid flipping interrupts. > get_cpu() > is not an alternative and the point is to avoid disabling interrupts > which is a much more expensive operation. > Agree with every word. Hillf
