Re: [PATCH 0/8] idle page tracking / working set estimation

Michel Lespinasse
2011-09-27T10:14:19Z

On Tue, Sep 27, 2011 at 3:03 AM, Balbir Singh <bsingharora@gmail.com> wrote:
> On Sat, Sep 17, 2011 at 9:09 AM, Michel Lespinasse <walken@google.com> wrote:
>> Patch 3 introduces page_referenced_kstaled(), which is similar to
>> page_referenced() but is used for idle page tracking rather than
>> for memory reclaimation. Since both functions clear the pte_young bits
>> and we don't want them to interfere with each other, two new page flags
>> are introduced that track when young pte references have been cleared by
>> each of the page_referenced variants.
>
> Sorry, I have trouble parsing this sentence, could you elaborate on "when"?

page_referenced() indicates if a page was accessed since the previous
page_referenced() call.

page_referenced_kstaled() indicates if a page was accessed since the
previous page_referenced_kstaled() call.

Both of the functions need to clear PTE young bits; however we don't
want the two functions to interfere with each other. To achieve this,
we add two page bits to indicate when a young PTE has been observed by
one of the functions but not by the other.

--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.