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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 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 X-Rspamd-Queue-Id: 68B6A160003 X-Rspam-User: X-Stat-Signature: bfnarzxy3pdk6s65bi5c51drq5p7xkoa X-Rspamd-Server: rspam07 X-HE-Tag: 1767824325-555676 X-HE-Meta: U2FsdGVkX19dn1xg5JHGQLkTCsR0szXyJemelYtKNSnvcMlf5j9KRT9qvyZqoSvOhxFI0NA1A1xnDn1zA3c2dznZiT1vtcErJFDv3YCrPOZRGqcMZb2fj6na6+R3dAU3FqqALkwdpsjvxVeIGmjkKouaT/HgClx4oqCw+ak9px8sqCR21UY8Ply6n831Bm/5RDjY7Six4uRPRWwUI/FRr8hEPeB/S5P4Lo68ezovO9bVONkV8IpoiQaN9YOeS6bAVsH///lJqKuyXFrg5LxtkiAY6vKsCksSPR7xJcxXeoheZeBdFoeonVzdH524jIKumQgzcZ8mPfLvny7HCB2klgaf6CbR/e1qLdrFJ7grrZw9lhcCSMI8nKr9hLdvNgvAA68NnAo71tVTw9D9mtjKpDDShqu8dqVwg1sjAZqczjJXAJHvy7iUBE6U6a6ihPEx/TDFxE0syyqicm356+YE+8Yr+3+MCy+9PmuMwYOZ0phVllNcU2N/BnT1puf9pIF4ikwZbN0/EVhLFwDWOmyhoO4+LSmpkXocttudusNX/dxVQh1fWGLm0mF28cTKjUGiNQVIm+NjriUA82xjNHYjF2YskAp2IM7oZuWF0wtyExZhTUu9jTMNl/L76PzyW5bFG5ZdhUZJTPdCY4E9/8fQGIfmPPo2HHlKtcw35H7gp83QxzG3uXYt2BQrPQP2OQ8ji63kGbKOqM9BkYg6yNpuOcH3NpZ129M3oHtsdRSJW6BO925cPOOKFT9eJX6WxPEG/Z8tSl9dyl5rWKmFwcpgVGSD6/MESaKLUJt7d7sri3Yc+NLTw+CjswMWUuxc7pJkhTuXoGO8qZfpe2OiD0ZJTl4eyhlQMLFGjTSM31ses5lzhHplsywI8FKstQJuPtVPbPQkPZzHYd0+inZpcz920gxkzWV+qMsmNEHVttXVaF9Z5hbTagSCI5UehxQNJueAC+eS/w6gPP93vj+Z5Ip ssFK6qhJ XDf4ip+isTETEu3/DAjhuwM+ouE2Dt3swc228bzYifRBPqZUvul0dHGyg7pjuIm52R9tEnLhUjtlEUFbun8Zf1ceHaJKUlWMkxedMLP3X2P0PQ6V3Ua5S2IlSw8HS7cAhHMAC4yWpvKhd8HAmectWLg9YTNFNAsrtyW+9rwMDH12ilCH0kOUymOf5H3p5lct0Os34OCHMJKs3qvcLd2UKZ2jVfyTkV08gdLeizhW3gi4JH3+AwrserEG+AXLEtL2fOzLDv6MjQ8Wqjvt9At12g9p/YZZMrSQQmmIkzJ2vfyNSHbDvzLQehhTH8YKkQPotoocDM/lLhIWs01TAGijJMEQ9g3hTbh+oCfeykSTa3Vxe82YcE+kIvesJPY/QJUA2qvq8 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 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