linux-kernel - Re: [RFC][Patch v12 1/2] mm: page

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Date:   Tue, 13 Aug 2019 06:42:41 -0400
From:   Nitesh Narayan Lal <nitesh@...hat.com>
To:     David Hildenbrand <david@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, virtio-dev@...ts.oasis-open.org,
        Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com,
        pagupta@...hat.com, wei.w.wang@...el.com,
        Yang Zhang <yang.zhang.wz@...il.com>,
        Rik van Riel <riel@...riel.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, dodgen@...gle.com,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        dhildenb@...hat.com, Andrea Arcangeli <aarcange@...hat.com>,
        john.starks@...rosoft.com, Dave Hansen <dave.hansen@...el.com>,
        Michal Hocko <mhocko@...e.com>, cohuck@...hat.com
Subject: Re: [RFC][Patch v12 1/2] mm: page_reporting: core infrastructure


On 8/13/19 6:34 AM, David Hildenbrand wrote:
>>>>> +static int process_free_page(struct page *page,
>>>>> +                            struct page_reporting_config *phconf, int count)
>>>>> +{
>>>>> +       int mt, order, ret = 0;
[...]
>>>>> +/**
>>>>> + * zone_reporting_init - For each zone initializes the page reporting fields
>>>>> + * and allocates the respective bitmap.
>>>>> + *
>>>>> + * This function returns 0 on successful initialization, -ENOMEM otherwise.
>>>>> + */
>>>>> +static int zone_reporting_init(void)
>>>>> +{
>>>>> +       struct zone *zone;
>>>>> +       int ret;
>>>>> +
>>>>> +       for_each_populated_zone(zone) {
>>>>> +#ifdef CONFIG_ZONE_DEVICE
>>>>> +               /* we can not report pages which are not in the buddy */
>>>>> +               if (zone_idx(zone) == ZONE_DEVICE)
>>>>> +                       continue;
>>>>> +#endif
>>>> I'm pretty sure this isn't needed since I don't think the ZONE_DEVICE
>>>> zone will be considered "populated".
>>>>
>>> I think you are right (although it's confusing, we will have present
>>> sections part of a zone but the zone has no present_pages - screams like
>>> a re factoring - leftover from ZONE_DEVICE introduction).
>>
>> I think in that case it is safe to have this check here.
>> What do you guys suggest?
> If it's not needed, I'd say drop it (eventually add a comment).


Comment to mention that we do not expect a zone with non-buddy page to be
initialized here?

>
>
-- 
Thanks
Nitesh