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Thu, 14 Nov 2024 10:42:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8kr9EwXUNWfCJgAAD6G6ig (envelope-from ); Thu, 14 Nov 2024 10:42:13 +0000 Message-ID: <80d61508-f714-4d4c-b8e1-b5c0db6adbdd@suse.cz> Date: Thu, 14 Nov 2024 11:42:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 11/57] fork: Permit boot-time THREAD_SIZE determination Content-Language: en-US To: Ryan Roberts , Andrew Morton , Andrey Ryabinin , Anshuman Khandual , Ard Biesheuvel , Arnd Bergmann , Catalin Marinas , David Hildenbrand , Greg Marsden , Ingo Molnar , Ivan Ivanov , Juri Lelli , Kalesh Singh , Marc Zyngier , Mark Rutland , Matthias Brugger , Miroslav Benes , Peter Zijlstra , Vincent Guittot , Will Deacon Cc: kasan-dev@googlegroups.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20241014105514.3206191-1-ryan.roberts@arm.com> <20241014105912.3207374-1-ryan.roberts@arm.com> <20241014105912.3207374-11-ryan.roberts@arm.com> From: Vlastimil Babka In-Reply-To: <20241014105912.3207374-11-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 9ia89jq76soi9fdaby7gqttanzx3iorc X-Rspamd-Queue-Id: 16EE6100014 X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1731580851-162729 X-HE-Meta: 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 PUv/EW5q ePdy4po43qYU+2rcWnZBnjKLYUP8CvrZJBPyNKIfESit7qqrqH5LhyCQqA2SHcbaeGpFTW+skWRR9YulwuMZ5Nd4JpHUOFJ4ndB41d0PTzHeKlJbVfpeiw45F8ybkFH/9hJ0N7XIp4PwAsL4bcBhH4b/kIfJM64TPqoB1U44dPdoAaMpvXqlSpc0SGwVpMjpZNMUPZo2wHimAdxOAXskl2TdubW/F0SbF5/UeAnO3XXoWXJSMIczZWt/WZo7OHkq+h6ADsdTpPkyv3jz003pYem3j2yWmPbogi7Z4O6kebGYnTGYqzWGbYSuMXUlb3Frdt69qLH2sSU5wSAnC7g4XZWl2VUtSbZE4/aHLyBymse4EeDfucczUSyRvsdtjUSfLPiNAtVHi/6I5mbZCcl9JVGwnb2qIhFo50SJ/C55wWypbErc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/14/24 12:58, Ryan Roberts wrote: > THREAD_SIZE defines the size of a kernel thread stack. To date, it has > been set at compile-time. However, when using vmap stacks, the size must > be a multiple of PAGE_SIZE, and given we are in the process of > supporting boot-time page size, we must also do the same for > THREAD_SIZE. > > The alternative would be to define THREAD_SIZE for the largest supported > page size, but this would waste memory when using a smaller page size. > For example, arm64 requires THREAD_SIZE to be 16K, but when using 64K > pages and a vmap stack, we must increase the size to 64K. If we required > 64K when 4K or 16K page size was in use, we would waste 48K per kernel > thread. > > So let's refactor to allow THREAD_SIZE to not be a compile-time > constant. THREAD_SIZE_MAX (and THREAD_ALIGN_MAX) are introduced to > manage the limits, as is done for PAGE_SIZE. > > When THREAD_SIZE is a compile-time constant, behaviour and code size > should be equivalent. > > Signed-off-by: Ryan Roberts Acked-by: Vlastimil Babka