Re: mm-more-likely-reclaim-madv_sequential-mappings.patch

[Johannes Weiner <hannes@saeurebad.de>]

Nick Piggin <nickpiggin@yahoo.com.au> writes:

>> >> Another access would mean another young PTE, which we will catch as a
>> >> proper reference sooner or later while walking the mappings, no?
>> >
>> > No. Another access could come via read/write, or be subsequently unmapped
>> > and put into PG_referenced.
>>
>> read/write use mark_page_accessed(), so after having two accesses, the
>> page is already active.  If it's not and we find an access through a
>> sequential mapping, we should be safe to clear PG_referenced.
>
> That's just handwaving. The patch still clears PG_referenced, which
> is a shared resource, and it is wrong, conceptually. You can't argue
> with that.
>
> What about if mark_page_accessed is only used on the page once? and
> it is referenced but not active?

I see the problem now, thanks for not giving up ;) Fixing up the fault
paths and moving their mark_page_accessed to the unmap side seems like a
good idea.

	Hannes

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