From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A1D7249659 for ; Wed, 7 Jan 2026 22:18:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767824324; cv=none; b=P7lBnG3O7zHmtBv7npNSbtR+t/MOG9EoU0HU8CrCGvc+HpN6kTgdot7tcm7H1joj1X97FO6K1yifI61K6fDOgoLNfCHQccwYNKHuDnaaJ8twiXb78uF/sB8cYTYjmPvzmIHmd41DUQcq6SP1OhWK8SWdo2VAQ90v2m/9RtDwXWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767824324; c=relaxed/simple; bh=KdSmcJ8/TbqJDKA+KiohOltt+WMWmZB4A/avr7C9dwU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UWYs7MAvXHod9spjA7VbGIGBykH8qQJc30sOgICKtWzwqsfefghnulHRCEWM6nZOyVXd/yIVHhrTe1zTaZKO4llHz+wsYA6y/zQU3Cd902nGWXMY5Ui9CCaDupvdqqqal6zQEFbyY1kSoust2+GWGKobOkRNyJO8nOjk5ISKbiQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dVZhRQgH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dVZhRQgH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9176C4CEF1; Wed, 7 Jan 2026 22:18:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767824324; bh=KdSmcJ8/TbqJDKA+KiohOltt+WMWmZB4A/avr7C9dwU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dVZhRQgHuDJIGIg7EvZ3XelD0Qfr9oo2XXWqcGHPyrrPtyW3TfZaFfLtyYdPvBLVG j1WFpfM8ryqsFh7rYijXsWjspzyckhUJ6cmJ/C5JF4c98VN1CKwbcGaP5Xv4e+zp5H 4NvVx2ZyOXeknhDsWgxG5xd60fzw/eZiwa165WiP2FP4nDqbAN0AuQtkCyc5dd5qfU 6CUp5ZLk13h5IIfUweXEhwJVqaPYFf7r63y0dqoIBo8gClms6lCDyvE6ukjBZdKasV un91N7u1v7HiSjeXEgCXWOl6rP5tzrCokKbMkb0mkLut2hheRLpWzoG95uN5wC9bjz NW+UF8w55kltw== Message-ID: Date: Wed, 7 Jan 2026 23:18:36 +0100 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 v11 8/8] mm: folio_zero_user: cache neighbouring pages To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: 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, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, chleroy@kernel.org, ioworker0@gmail.com, lizhe.67@bytedance.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20260107072009.1615991-1-ankur.a.arora@oracle.com> <20260107072009.1615991-9-ankur.a.arora@oracle.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/7/26 08:20, Ankur Arora wrote: > folio_zero_user() does straight zeroing without caring about > temporal locality for caches. > > This replaced commit c6ddfb6c5890 ("mm, clear_huge_page: move order > algorithm into a separate function") where we cleared a page at a > time converging to the faulting page from the left and the right. > > To retain limited temporal locality, split the clearing in three > parts: the faulting page and its immediate neighbourhood, and the > regions on its left and right. We clear the local neighbourhood last > to maximize chances of it sticking around in the cache. > > Performance > === > > AMD Genoa (EPYC 9J14, cpus=2 sockets * 96 cores * 2 threads, > memory=2.2 TB, L1d=16K/thread, L2=512K/thread, L3=2MB/thread) > > vm-scalability/anon-w-seq-hugetlb: this workload runs with 384 processes > (one for each CPU) each zeroing anonymously mapped hugetlb memory which > is then accessed sequentially. > stime utime > > discontiguous-page 1739.93 ( +- 6.15% ) 1016.61 ( +- 4.75% ) > contiguous-page 1853.70 ( +- 2.51% ) 1187.13 ( +- 3.50% ) > batched-pages 1756.75 ( +- 2.98% ) 1133.32 ( +- 4.89% ) > neighbourhood-last 1725.18 ( +- 4.59% ) 1123.78 ( +- 7.38% ) > > Both stime and utime largely respond somewhat expectedly. There is a > fair amount of run to run variation but the general trend is that the > stime drops and utime increases. There are a few oddities, like > contiguous-page performing very differently from batched-pages. > > As such this is likely an uncommon pattern where we saturate the memory > bandwidth (since all CPUs are running the test) and at the same time > are cache constrained because we access the entire region. > > Kernel make (make -j 12 bzImage): > > stime utime > > discontiguous-page 199.29 ( +- 0.63% ) 1431.67 ( +- .04% ) > contiguous-page 193.76 ( +- 0.58% ) 1433.60 ( +- .05% ) > batched-pages 193.92 ( +- 0.76% ) 1431.04 ( +- .08% ) > neighbourhood-last 194.46 ( +- 0.68% ) 1431.51 ( +- .06% ) > > For make the utime stays relatively flat with a fairly small (-2.4%) > improvement in the stime. > > Signed-off-by: Ankur Arora > Reviewed-by: Raghavendra K T > Tested-by: Raghavendra K T > --- Nothing jumped at me, thanks! Acked-by: David Hildenbrand (Red Hat) -- Cheers David