Re: [PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file_rss

Minchan Kim
2010-01-04T00:49:48Z

On Thu, Dec 31, 2009 at 5:43 PM, Hugh Dickins
<hugh.dickins@tiscali.co.uk> wrote:
> On Thu, 31 Dec 2009, Minchan Kim wrote:
>> On Thu, Dec 31, 2009 at 1:49 AM, Hugh Dickins
>> <hugh.dickins@tiscali.co.uk> wrote:
>> >
>> > You are right that I completely overlooked the issue of whether to
>> > include the ZERO_PAGE in rss counts (now being a !vm_normal_page,
>> > it was just natural to leave it out); and I overlooked the fact that
>> > it used to be counted into file_rss in the old days (being !PageAnon).
>> >
>> > So I'm certainly at fault for that, and thank you for bringing the
>> > issue to attention; but once considered, I can't actually see a good
>> > reason why we should add code to count ZERO_PAGEs into file_rss now.
>> > And if this patch falls, then 1/3 and 3/3 would fall also.
>> >
>> > And the patch below would be incomplete anyway, wouldn't it?
>> > There would need to be a matching change to zap_pte_range(),
>> > but I don't see that.
>>
>> Thanks.
>> If we think this patch is need, I will repost path with fix it.
>>
>> What do you think?
>
> If someone comes up with a convincing case in which their system
> is behaving significantly worse because the zero page is not being
> counted in rss now, then we shall probably want your patch.
> But I still don't yet see a reason to add code just to keep the
> anon_rss+file_rss number looking the same as it was before, in this
> exceptional case where there's a significant number of zero pages.

Okay. I understand your point.
I will repost this patch when we need this. :)
Thanks for careful review, Hugh.

>
> Hugh
>

--
Kind regards,
Minchan Kim