Re: page migration patchset

[Steve Longerbeam <stevel@mvista.com>]

Ray Bryant wrote:

> Steve Longerbeam wrote:
>
>
>>
>> isn't this already taken care of? read_swap_cache_async() is given
>> a vma, and passes it to alloc_page_vma(). So if you have earlier
>> changed the policy for that vma, the new policy will be used
>> when allocating the page during the swap in.
>>
>> Steve
>>
>
> What if the policy associated with a vma is the default policy?


then read_swap_cache_async() would probably allocate pages for
the swap readin from the wrong nodes, but then migrate_process_pages
would move those to the correct nodes later. But if migrate_process_pages
is called *before* swap readin, the policies will be changed and
read_swap_cache_async() would allocate from the correct nodes.

Maybe I'm missing something, but let me rephrase my argument.
If read_swap_cache_async() is called *before* the vma policies are
changed, they will most likely be allocated from the wrong nodes but
will then be migrated to the correct nodes during the
policy-change-and-page-migrate syscall, and if the swap readin happens
*after* the syscall, the page allocations will use the new policies.

Steve