Re: [PATCH] mm: mlock: remove lru_add_drain_all()

[Shakeel Butt <shakeelb@google.com>]

On Thu, Oct 19, 2017 at 1:13 PM, Michal Hocko <mhocko@kernel.org> wrote:
> On Thu 19-10-17 12:46:50, Shakeel Butt wrote:
>> > [...]
>> >>
>> >> Sorry for the confusion. I wanted to say that if the pages which are
>> >> being mlocked are on caches of remote cpus then lru_add_drain_all will
>> >> move them to their corresponding LRUs and then remaining functionality
>> >> of mlock will move them again from their evictable LRUs to unevictable
>> >> LRU.
>> >
>> > yes, but the point is that we are draining pages which might be not
>> > directly related to pages which _will_ be mlocked by the syscall. In
>> > fact those will stay on the cache. This is the primary reason why this
>> > draining doesn't make much sense.
>> >
>> > Or am I still misunderstanding what you are saying here?
>> >
>>
>> lru_add_drain_all() will drain everything irrespective if those pages
>> are being mlocked or not.
>
> yes, let me be more specific. lru_add_drain_all will drain everything
> that has been cached at the time mlock is called. And that is not really
> related to the memory which will be faulted in (and cached) and mlocked
> by the syscall itself. Does it make more sense now?
>

Yes, you are absolutely right. Sorry for the confusion.

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