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[2003:cb:c705:4c00:486:38e2:8ff8:a135]) by smtp.gmail.com with ESMTPSA id j7-20020adfb307000000b002be063f6820sm4904478wrd.81.2023.01.25.02.20.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Jan 2023 02:20:04 -0800 (PST) Message-ID: <477bbc1e-a60a-cfce-d31e-0b4bdd5f6429@redhat.com> Date: Wed, 25 Jan 2023 11:20:03 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH mm-unstable v2 1/6] mm: Add folio_estimated_mapcount() Content-Language: en-US To: "Vishal Moola (Oracle)" , linux-mm@kvack.org Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org References: <20230124012210.13963-1-vishal.moola@gmail.com> <20230124012210.13963-2-vishal.moola@gmail.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230124012210.13963-2-vishal.moola@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.01.23 02:22, Vishal Moola (Oracle) wrote: > folio_estimated_mapcount() takes in a folio and calls page_mapcount() on > the first page of that folio. > > This is necessary for folio conversions where we only care about either the > entire_mapcount of a large folio, or the mapcount of a not large folio. > > This is in contrast to folio_mapcount() which calculates the total > number of the times a folio and its subpages are mapped. > > Signed-off-by: Vishal Moola (Oracle) > --- > include/linux/mm.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index c9db257f09b3..543c360f7ecc 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -875,6 +875,11 @@ static inline int page_mapcount(struct page *page) > return mapcount; > } > > +static inline int folio_estimated_mapcount(struct folio *folio) > +{ > + return page_mapcount(folio_page(folio, 0)); > +} > + > int folio_total_mapcount(struct folio *folio); > > /** I'm sorry, but "estimated" as absolutely unclear semantics. You could have a THP mapped into 9999 processes using THP and the estimation would be "0". Huh? Absolutely unclear and confusing. No thanks. -- Thanks, David / dhildenb