linux-kernel - Re: [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid

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Date:   Wed, 17 Mar 2021 16:03:06 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from
 pfn_range_valid_contig

On Wed 17-03-21 15:36:35, David Hildenbrand wrote:
> On 17.03.21 15:31, Michal Hocko wrote:
> > On Wed 17-03-21 12:12:51, Oscar Salvador wrote:
> > > pfn_range_valid_contig() bails out when it finds an in-use page or a
> > > hugetlb page, among other things.
> > > We can drop the in-use page check since __alloc_contig_pages can migrate
> > > away those pages, and the hugetlb page check can go too since
> > > isolate_migratepages_range is now capable of dealing with hugetlb pages.
> > > Either way, those checks are racy so let the end function handle it
> > > when the time comes.
> > 
> > I haven't realized PageHuge check is done this early. This means that
> > previous patches are not actually active until now which is not really
> > greate for bisectability. Can we remove the HugePage check earlier?
> 
> alloc_contig_pages() vs. alloc_contig_range(). The patches are active for
> virtio-mem and CMA AFAIKS.

yeah, I meant to say "are not actually fully active".
-- 
Michal Hocko
SUSE Labs