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

[Johannes Weiner <hannes@saeurebad.de>]

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

> On Friday 17 October 2008 04:04, Rik van Riel wrote:
>> Nick Piggin wrote:
>> > ClearPageReferenced I don't know if it should be cleared like this.
>> > PageReferenced is more of a bit for the mark_page_accessed state machine,
>> > rather than the pte_young stuff. Although when unmapping, the latter
>> > somewhat collapses back to the former, but I don't know if there is a
>> > very good reason to fiddle with it here.
>> >
>> > Ignoring the young bit in the pte for sequential hint maybe is OK (and
>> > seems to be effective as per the benchmarks). But I would prefer not to
>> > merge the PageReferenced parts unless they get their own justification.
>>
>> Unless we clear the PageReferenced bit, we will still activate
>> the page - even if its only access came through a sequential
>> mapping.
>>
>> Faulting the page into the sequential mapping ends up setting
>> PageReferenced, IIRC.
>
> Yes I see. But that's stupid because then you can end up putting a
> sequential mapping on a page, and cause that to deactivate somebody
> else's references... and the deactivation _only_ happens if the
> sequential mapping pte is young and the page happens not to be
> active, which is totally arbitrary.

Another access would mean another young PTE, which we will catch as a
proper reference sooner or later while walking the mappings, no?

	Hannes

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