Re: [PATCH 2/3] memory-hotplug: more general validation of zone during online

From: Yasuaki Ishimatsu
Date: Wed May 11 2016 - 11:18:26 EST



On Tue, 10 May 2016 15:39:43 -0500
Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx> wrote:

> On Tue, May 10, 2016 at 11:08:56AM -0700, Yasuaki Ishimatsu wrote:
> >On Mon, 9 May 2016 12:53:38 -0500
> >Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx> wrote:
> >> * If X is lower than Y, the onlined memory must lie at the end of X.
> >> * If X is higher than Y, the onlined memory must lie at the start of X.
> >
> >If memory address has hole, memory address gets uncotinuous. Then memory
> >cannot be changed the zone by above the two conditions. So the conditions
> >shouold be removed.
>
> I don't understand what you mean by this. Could you give an example?

> +int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
> + enum zone_type target)
> +{
<snip>
> + if (idx < target) {
> + /* pages must be at end of current zone */
> + if (pfn + nr_pages != zone_end_pfn(zone))
> + return 0;
<snip>
> + if (target < idx) {
> + /* pages must be at beginning of current zone */
> + if (pfn != zone->zone_start_pfn)
> + return 0;

According your patch, memory address must be continuous for changing zone.
So if memory address is uncontinuous as follows, memory address 0x180000000-0x1FFFFFFFF
can be changed from ZONE_NORMAL to ZONE_MOVABLE. But memory address 0x80000000-0xFFFFFFFF
can not be changed from ZONE_NORMAL to ZONE_MOVABLE since it does not meet
above condition.

Memory address
0x80000000 - 0xFFFFFFFF
0x180000000 - 0x1FFFFFFFF

Thanks,
Yasuaki Ishimatsu