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SubjectRe: [PATCH v5 2/6] ksm: support unsharing zero pages placed by KSM
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On 04.02.23 07:18, yang.yang29@zte.com.cn wrote:

[sorry, was on vacation last week]

>> Why use flags if they both conditions are mutually exclusive?
>
> Just to make the return value of break_ksm_pmd_entry() more expressive and
> understandable. because break_ksm_pmd_entry have three types of returned
> values (0, 1, 2).

It adds confusion. Just simplify it please.

>
>> MADV_UNMERGEABLE -> unmerge_ksm_pages() will never unshare the shared
>> zeropage? I thought the patch description mentions that that is one of
>> the goals?
>
> No, MADV_UNMERGEABLE will trigger KSM to unshare the shared zeropages in the
> context of "get_next_rmap_item() -> unshare_zero_pages(), but not directly in the
> context of " madvise()-> unmerge_ksm_pages() ". The reason for this is to avoid
> increasing long delays of madvise() calling on unsharing zero pages.
>

Why do we care and make this case special?

--
Thanks,

David / dhildenb

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