Re: [PATCH 00/10] fix freepage count problems due to memory isolation

[Vlastimil Babka]

On 07/17/2014 08:12 AM, Joonsoo Kim wrote:
> > Hm I see. So what if it wasn't a special pcplist, but a special "free list"
> > where the pages would be just linked together as on pcplist, regardless of
> > order, and would not merge until the CPU that drives the memory isolation
> > process decides it is safe to flush them away. That would remove the need for
> > IPI's and provide the same guarantees I think.
>
> Looks good. It would work. I think that your solution is better than mine.
> I will implement it and test.

Thanks. But maybe there's still a good use for marking pages specially 
as isolated, and not PageBuddy with freepage_migratetype set to 
MIGRATE_ISOLATE. Why do we buddy-merge them anyway? I don't think CMA or 
memory offlining benefits from that, and it only makes the code more 
complex?
So maybe we could split isolated buddy pages to order-0 marked as 
PageIsolated and have a single per-zone list instead of order-based 
freelists?

> > Do we really need to check PageBuddy()? Could a page get marked as PageIsolate()
> > but still go to normal list instead of isolate list?
>
> Checking PageBuddy() is used for identifying page linked in normal
> list.

Ah right, forgot it walks by pfn scanning, not by traversing the free list.

> Thanks.
>
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