Nhat Pham <nphamcs@xxxxxxxxx> writes:
> On Tue, Sep 24, 2024 at 6:53 PM Baolin Wang
> <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>>
>>
>> One benefit I can mention is that removing 'SWAP_MAP_SHMEM' can help to
>> batch free shmem swap entries in __swap_entries_free(), similar to the
>> commit bea67dcc5eea ("mm: attempt to batch free swap entries for
>> zap_pte_range()") did, which can improve the performance of shmem mTHP
>> munmap() function based on my testing.
>
> Yeah, the problem with having an extraneous state is you have to
> constantly check for it in code, and/or keep it in mind when you
> develop things. I've been constantly having to check for this state
> when I develop code around this area, and it gets old fast.
>
> If we can use it to optimize something, I can understand keeping it.
> But it just seems like dead code to me :)
>
> My preference is to do this as simply as possible - add another case
> (usage == 1, nr > 1, and we need to add swap continuations) in the
> check in __swap_duplicate()'s first loop, and just WARN right there.
>
> That case CANNOT happen UNLESS we introduce a bug, or have a new use
> case. When we actually have a use case, we can always introduce
> handling/fallback logic for that case.
>
> Barry, Yosry, Baolin, Ying, how do you feel about this?
Sounds good to me to just WARN now. We can always improve when it's
necessary.
--
Best Regards,
Huang, Ying
