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? get_cpu() is not an alternative and the point is to avoid disabling interrupts which is a much more expensive operation. -- Mel Gorman SUSE Labs
