linux-kernel - Re: [PATCH RFC 15/39] mm/huge_memory: batch rmap operations in __split_huge_pmd

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Message-ID: <873e12ec-c153-445c-aaa3-a68c59a01fe8@redhat.com>
Date:   Tue, 5 Dec 2023 13:26:50 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Ryan Roberts <ryan.roberts@....com>, linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH RFC 15/39] mm/huge_memory: batch rmap operations in
 __split_huge_pmd_locked()

On 05.12.23 13:22, Ryan Roberts wrote:
> On 04/12/2023 14:21, David Hildenbrand wrote:
>> Let's use folio_add_anon_rmap_ptes(), batching the rmap operations.
>>
>> While at it, use more folio operations (but only in the code branch we're
>> touching), use VM_WARN_ON_FOLIO(), and pass RMAP_COMPOUND instead of
> 
> You mean RMAP_EXCLUSIVE?

Indeed.

[...]

>> -		if (!freeze)
>> -			page_ref_add(page, HPAGE_PMD_NR - 1);
>> +		if (!freeze) {
>> +			rmap_t rmap_flags = RMAP_NONE;
>> +
>> +			folio_ref_add(folio, HPAGE_PMD_NR - 1);
>> +			if (anon_exclusive)
>> +				rmap_flags = RMAP_EXCLUSIVE;
> 
> nit: I'd be inclined to make this |= since you're accumulating optional falgs.
> Yes, its the only one so it still works as is...


Make sense!

-- 
Cheers,

David / dhildenb