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b=aHxuvZtc8P9UeTJfS021vS1NUxKIeuMkXI5RU0z5dIYjl8Go8g6mGvRPGZmX1VOrW go9gUSKU8K9e/u7kbqBqw/TSMz9Jw5RmCrgSq/CkFlu7+c2OQ4ciQWRoosbL5zAo3A TgpkT43Bu09XDBxrOa9a9N80xSIR7o52tjDxg7uk0aQMuwq1aLVFK9rNEtd8Mz+qHn 79bn0cBSEiP/FTm8YKUky7qkTKrsNKILMrwvobon2G8UvOfl6GkoTiSxLzjIyyLDsk QnqYpT5itVfydMgw6MytOHqFeokcasdlCXsaiwvPYxpcPweKD5gfL7ybkATh9zLUWn GTU3NUdDwTbHA== Message-ID: <1bc39fcf-6fb1-49a9-a30a-8289ed9a524d@kernel.org> Date: Wed, 19 Aug 2026 09:44:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/8] Optimize anonymous swapbacked large folio unmapping To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, hughd@google.com, chrisl@kernel.org, kasong@tencent.com Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, baohua@kernel.org, youngjun.park@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260723070905.3422276-1-dev.jain@arm.com> <80632d25-df40-475b-b7d0-912d657a977e@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: gz3z45p7zzqhx3sxhzfojtt9n64hoy5q X-Rspamd-Queue-Id: 2B4E720004 X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1787125505-357277 X-HE-Meta: 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 modfPN03 Jv2rY/E0qKvRSlhJMephB7M7Td5dhs2+4SCSLKKd6Z8205fSucQ24KKBljgdkUrOjd/RmJjnZMi3wf7J+VOMOIO77JrTOoI+NYAvzpKDCppIZy26MqESaJGzTgLEGwkqw8sPySKqinh6KpM3AhZbDniYZZWYzl08h386ZNG4bikTV8sqwnvyXXec4TqQGxkaVTurGPBvA1KwPUKlsdXhR6mgr88T/Kc9PmkjjrG12Y9xEiXHZ7r3KaFDlpWmjn91ZSLyh Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/19/26 08:50, Dev Jain wrote: > > > On 23/07/26 12:38 pm, Dev Jain wrote: >> Speed up unmapping of anonymous swapbacked large folios by clearing >> the ptes, and setting swap ptes, in one go. >> >> The following benchmark (stolen from Barry) is used to measure the >> time taken to swapout 256M worth of memory backed by 64K large folios: >> >> #define _GNU_SOURCE >> #include >> #include >> #include >> #include >> #include >> #include >> #include >> >> #define SIZE_MB 256 >> #define SIZE_BYTES (SIZE_MB * 1024 * 1024) >> >> int main() { >> void *addr = mmap(NULL, SIZE_BYTES, PROT_READ | PROT_WRITE, >> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); >> if (addr == MAP_FAILED) { >> perror("mmap failed"); >> return 1; >> } >> >> memset(addr, 0, SIZE_BYTES); >> >> struct timespec start, end; >> clock_gettime(CLOCK_MONOTONIC, &start); >> >> if (madvise(addr, SIZE_BYTES, MADV_PAGEOUT) != 0) { >> perror("madvise(MADV_PAGEOUT) failed"); >> munmap(addr, SIZE_BYTES); >> return 1; >> } >> >> clock_gettime(CLOCK_MONOTONIC, &end); >> >> long duration_ns = (end.tv_sec - start.tv_sec) * 1e9 + >> (end.tv_nsec - start.tv_nsec); >> printf("madvise(MADV_PAGEOUT) took %ld ns (%.3f ms)\n", >> duration_ns, duration_ns / 1e6); >> >> munmap(addr, SIZE_BYTES); >> return 0; >> } >> >> Performance as measured on a Linux VM on Apple M3 (arm64): >> >> Vanilla - Mean: 37401913 ns, std dev: 12% >> Patched - Mean: 17420282 ns, std dev: 11% >> >> resulting in more than 2x speedup. >> >> No regression observed on 4K folios. >> >> Performance as measured on bare metal x86: >> >> Vanilla - mean: 54986286 ns, std dev: 1.5% >> Patched - mean: 51930795 ns, std dev: 3% >> >> I tried magnifying the difference on x86 by using 1M large folios, but >> can't spot an obvious improvement (looks like my system is too fast to >> benefit from batched atomic operations!), hinting that the benefit lies >> mainly in the reduction of ptep_get() calls and the reduction of TLB >> flushes during contpte-unfolding, on arm64. >> >> No regression is observed on 4K folios on x86 too. >> >> --- > > > Hi Andrew, > > I am not sure what is the current process in mm regarding sending patches during > merge window - would you prefer seeing v2 after merge window or shall I respin? > > Let's wait for more review first. Most of the patches have not been reviewed and there is no time to rush at this point. -- Cheers, David