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SubjectRe: [PATCH -V7 RESEND 08/21] swap: Support to read a huge swap cluster for swapin a THP
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Daniel Jordan <daniel.m.jordan@oracle.com> writes:

> On Sat, Dec 01, 2018 at 08:34:06AM +0800, Huang, Ying wrote:
>> Daniel Jordan <daniel.m.jordan@oracle.com> writes:
>> > What do you think?
>>
>> I think that swapoff() which is the main user of try_to_unuse() isn't a
>> common operation in practical. So it's not necessary to make it more
>> complex for this.
>
> Ok, probably not worth the surgery on try_to_unuse, even if swapoff can be
> expensive when it does happen.
>
>> In alloc_hugepage_direct_gfpmask(), the only information provided by vma
>> is: vma->flags & VM_HUGEPAGE. Because we have no vma available, I think
>> it is OK to just assume that the flag is cleared. That is, rely on
>> system-wide THP settings only.
>>
>> What do you think about this proposal?
>
> Sounds like a good compromise.
>
> So alloc_hugepage_direct_gfpmask will learn to make 'vma' optional? Slightly
> concerned that future callers that should be passing vma's might not and open a
> way to ignore vma huge page hints, but probably not a big deal in practice.

alloc_pages_vma() -> get_vma_policy() -> __get_vma_policy()

has done that already. So I guess that's not a big issue. The callers
should be careful.

Best Regards,
Huang, Ying

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