Re: [PATCH 3/3] vmevent: Implement special low-memory attribute

[KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>]

>> If we'll give up on "1." (Pekka, ping), then we need to solve "2."
>> in a sane way: we'll have to add a 'NR_FILE_PAGES - NR_SHMEM -
>> <todo-locked-file-pages>' attribute, and give it a name.
>
> Well, no, we can't give up on (1) completely. That'd mean that
> eventually we'd need to change the ABI and break userspace. The
> difference between exposing internal details and reasonable
> abstractions is by no means black and white.
>
> AFAICT, RECLAIMABLE_CACHE_PAGES is a reasonable thing to support. Can
> anyone come up with a reason why we couldn't do that in the future?

It can. but the problem is, that is completely useless. Because of, 1)
dirty pages writing-out
is sometimes very slow and 2) libc and some important library's pages
are critical important
for running a system even though it is clean and reclaimable. In other
word, kernel don't have
an info then can't expose it.

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