linux-kernel - Re: [PATCH v4 0/4] Make alloc_contig

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Message-ID: <20210315102740.GB25101@linux>
Date:   Mon, 15 Mar 2021 11:27:40 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v4 0/4] Make alloc_contig_range handle Hugetlb pages

On Mon, Mar 15, 2021 at 10:06:40AM +0100, David Hildenbrand wrote:
> 
> BTW, I stumbled yesterday over
> 
> alloc_contig_pages()->pfn_range_valid_contig():
> 
> 	if (page_count(page) > 0)
> 		rerurn false;
> 	if (PageHuge(page))
> 		return false;
> 
> As used by memtrace and for gigantic pages. We can now
> 
> a) Drop these check completely, as it's best-effort only and racy.
> alloc_contig_pages()/alloc_contig_range() will handle it properly.
> 
> b) Similarly, check for gigantic pages and/or movability/migratability.
> 
> Dropping both checks might be the right thing to do: might significantly
> increase allocation chances -- as we actually end up migrating busy pages
> ...

Oh, sorry David, my mail client tricked me and I did not see this till now.

I will have a look, but I would like to collect some more feedback from all
pieces before going any further and write a new version.
Vlastimil patch#1 and patch#2 and he was ok with them, but let see what others
think as well.

 

-- 
Oscar Salvador
SUSE L3