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[2003:d8:2f0a:2e00:89cb:c7f0:82f2:e43c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454d511bd78sm95925055e9.35.2025.07.11.12.14.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Jul 2025 12:14:51 -0700 (PDT) Message-ID: <2c6db237-3d64-43f5-8a20-168be5b248c8@redhat.com> Date: Fri, 11 Jul 2025 21:14:50 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 12/14] mm: add config option for clearing page-extents To: Ankur Arora Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20250710005926.1159009-1-ankur.a.arora@oracle.com> <20250710005926.1159009-13-ankur.a.arora@oracle.com> <878qkuprku.fsf@oracle.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11.07.25 19:25, Ankur Arora wrote: > > David Hildenbrand writes: > >> On 10.07.25 02:59, Ankur Arora wrote: >>> Add CONFIG_CLEAR_PAGE_EXTENT to allow clearing of page-extents >>> where architecturally supported. >>> This is only available with !CONFIG_HIGHMEM because the intent is to >>> use architecture support to clear contiguous extents in a single >>> operation (ex. via FEAT_MOPS on arm64, string instructions on x86) >>> which excludes any possibility of interspersing kmap()/kunmap(). >>> Signed-off-by: Ankur Arora >>> --- >>> mm/Kconfig | 9 +++++++++ >>> 1 file changed, 9 insertions(+) >>> diff --git a/mm/Kconfig b/mm/Kconfig >>> index 781be3240e21..a74a5e02de28 100644 >>> --- a/mm/Kconfig >>> +++ b/mm/Kconfig >>> @@ -910,6 +910,15 @@ config NO_PAGE_MAPCOUNT >>> endif # TRANSPARENT_HUGEPAGE >>> +config CLEAR_PAGE_EXTENT >>> + def_bool y >>> + depends on !HIGHMEM && ARCH_HAS_CLEAR_PAGES >>> + depends on TRANSPARENT_HUGEPAGE || HUGETLBFS >>> + >>> + help >>> + Use architectural support for clear_pages() to zero page-extents. >>> + This is likely to be faster than zeroing page-at-a-time. >>> + >> >> IIRC, adding a help text will make this option be configurable by the user, no? > > I tried changing the value in the generated .config by hand and that > reverted back to the computed value. So, I think this isn't configurable > by the user. Yes, I misremembered and the help text confused me. So yes, the help text in that case (internal entries) is uncommon (no need to guide the user when there are no options :) ), but feel free to keep it for documentation purposes. (e.g., HAVE_64BIT_ALIGNED_ACCESS does that) Maybe we should call it similarly HAVE_... to make it clearer that there are really no options. But I'm bad at #kconfig, so whatever you prefer. -- Cheers, David / dhildenb