Re: [PATCH 01/18] mm, hugetlb: protect reserved pages whensoftofflining requests the pages

From: Hillf Danton
Date: Tue Jul 30 2013 - 22:49:34 EST


On Wed, Jul 31, 2013 at 10:27 AM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote:
> On Mon, Jul 29, 2013 at 03:24:46PM +0800, Hillf Danton wrote:
>> On Mon, Jul 29, 2013 at 1:31 PM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote:
>> > alloc_huge_page_node() use dequeue_huge_page_node() without
>> > any validation check, so it can steal reserved page unconditionally.
>>
>> Well, why is it illegal to use reserved page here?
>
> If we use reserved page here, other processes which are promised to use
> enough hugepages cannot get enough hugepages and can die. This is
> unexpected result to them.
>
But, how do you determine that a huge page is requested by a process
that is not allowed to use reserved pages?
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