From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CD5938D006 for ; Wed, 19 Aug 2026 07:45:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787125507; cv=none; b=ToS/hVqMaeTreWh2zFDQRIDcCc03sHOiDhXQKi4vddGsHYhfvzNYzAvVZIoj0W0bxIlS3IE0BIHQz2n2F3f5ArJNXAg43sav6SG4OLuHzPw/T6FYF8dPyEcNeEci590NMIBOMMfxHoH/g+fVLumtT2BRGI/IG+ZVYyd74mZTiG0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787125507; c=relaxed/simple; bh=awQCYi+4JXqnyXqrldF46HNKZs+ah+1SZtdzsbn5fyA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dmar44pBk9h9CgcRGvMKEqsg9LkrPBm5MqG3cyE/JaoZwgPr/7Mbo0vq4WEXzhz8lcT6k0ZPeKb+3Z4oyyE3yizOTXiLGvmuPQ+l+WqnRubdb86j+SyvaB8Q3HybE9oss9MzsB3l0MWEPUawhd4wbnsWOZcilgJ+0ud1rpEoEJc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aHxuvZtc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aHxuvZtc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2570A1F000E9; Wed, 19 Aug 2026 07:44:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787125504; bh=sUGls/TPzkFWI3c1olei1087Mv7gZNyunUb3au02oYU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; 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 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 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 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