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b=HV43c7mjIDeIbR6rJ6DmEFmebk89gayz4U3b4977zb4IsxkfMKTJnsgb8kOTzbtBH 3sRxpVf1NqpYvK+4hsZZdWs+4xUKHJJQDRh/T5IQB0/SZLgARGq6r7X900y7z7L9Bg JhWRBs69MY9kdC4GddcjVRtqJuHjtxOOEJOSek2Rlh/xzpqajmIxKSGIGlocj+Lukc duUV+RdbYvAoemu5+ebwD2iUCYAijKLBRHMDoTpHy+rjBGUfY2V5wizO8J40FMEtEa 5IFc5sc2l5Xl645PotbsorN7wdTWKHrKLFUhT+1+IcGmOR2tIVpYTWw+o8D75kON5k tnPjL2LTuDQBg== Message-ID: Date: Tue, 12 May 2026 10:58:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm/page_alloc: replace kernel_init_pages() with batch page clearing To: Hrushikesh Salunke , akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, rkodsara@amd.com, bharata@amd.com, ankur.a.arora@oracle.com, shivankg@amd.com References: <20260504063942.553438-1-hsalunke@amd.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-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9D5521C000B X-Stat-Signature: 7dq1wjfkek6gghzjohfqzyu8e5qrwmrq X-Rspam-User: X-HE-Tag: 1778576341-18183 X-HE-Meta: U2FsdGVkX18XJP+xYGOmSNVe0Ac1ru7KLIsHiU6thGQ9t3ib1nCBPMmHNFzXMlKLmDo3/YrQc3utf0DgmTuul/c4epGiOXbvkJvpx2v8bSzau8LIGVaady0gUXYIFFu6G6uw6wVxaW3bWXsBxiNgGsRpgaWLpYbSGgftwkCp7WxprVYe/tQLTErH13ZIGSq15fosIzqm/SMIWRrKOkZ9nlK4rax/UvWKpmOP5WBauk1NC5wTCtt2ZDbPV0sAkpl/F7SkrbSTRSroqROJel9rO3yweORtC3w97myhxmIEa9NnNShb/92Oj8VdkLzsP2xjM25GjTj9iFwgTS4d43yXjVMh04zmbi6I/zI0Cl6n+6rRDpT9gnVpIjZbEeg+sjRP49ZFUte3BV3HyKSH2ebmXdt5Dg3OG7xSK6UaNOOsLN9NI4w7UUft4o/L56ttqkOYCvUjEOR21ynTYZhcNmj/EZ5Ri1JkOFBfydS7Mq+YYm5bm641SeXkVa5fcat+ifApu79ai71905pEOAodxqYoxYxyj3Ohe0DYa7g/it7+SDP855AdClAqmW2AdjeVSIS6bsSrHiRL8Ie/qwErU7D8ZAxPs+jQfiKdf+i8NHt6sBFS3B/6vh/zahxm3FR9bqljDb3pqzzC66H8w217G0rj4P7E7Z8G/8ZD6jUjPZJuStwfUjv2TDdFvZ+gDa+JL5oS2sGpEaQRgG9uXShSu3/tCEzmUjXpdHFi6izOITst4nZch4K5+5kXz6JK/ygFAigriNthKifV8StM+OJ1gkH9+agQqkZvj8ggtXn8qbe96mErUTA6IXXcZ/fbVYblq41vb4Cm6t+m/ConVxysqVDSPj5JMlrhTT83+v7dLINZt3MA9LFcmCJGMk1WAE7iNq05YmKETmIUDDWDzn24xgecn9n25xlmxvCZ33ajWDsyA9h5hc4lecvBOHFpBULPTxGy5s3TRjJetowBOG/49jh Fb8cLLXm Q/RmNf0mDQvTvYaviYXGnQ6ISXdMb9iFukka/jDgqg+hc+JaG4MzuErZ1tyrXu9v1pgC019OIa0UK1C5LIu5KmQu2t/WcDaQ0K5gjqweBkqM9KSv6krDrHlreMELbXTySLKEsTmGZ08NMVam8+log1GcCorNTGZhyh4Lq60Yv9gsQmApg3EXqetV7V3TtqKo/8j6Tk0P3E2apuky3mT67s1Dnfxz1/O0OpXfgVPyiRb2czdbTitP3+iMm2MUre/6uuFBu9Dwv58jYdBPO6Ubi3U/8PZWsMI+C2GSJOm1NAJcfBz6rcK2V4bX1YYZ6QW5YuBC0ls2n8WpLR4/xk0/0mZ0FLiEA9r1Q79IbzlCEYMC8huRZ4D5D13cAVtdPWCuJIpZS Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/4/26 08:39, Hrushikesh Salunke wrote: > When init_on_alloc is enabled, kernel_init_pages() clears every page > one at a time via clear_highpage_kasan_tagged(), which incurs per-page > kmap_local_page()/kunmap_local() overhead and prevents the architecture > clearing primitive from operating on contiguous ranges. > > Introduce clear_highpages_kasan_tagged() as a static batch clearing > helper in page_alloc.c that calls clear_pages() for the full contiguous > range on !HIGHMEM systems, bypassing the per-page kmap overhead and > allowing a single invocation of the arch clearing primitive across the > entire allocation. The HIGHMEM path falls back to per-page clearing > since those pages require kmap. > > Replace kernel_init_pages() with direct calls to the new helper, as it > becomes a trivial wrapper. > > Allocating 8192 x 2MB HugeTLB pages (16GB) with init_on_alloc=1: > > Before: 0.445s > After: 0.166s (-62.7%, 2.68x faster) > > Kernel time (sys) reduction per workload with init_on_alloc=1: > > Workload Before After Change > Graph500 64C128T 30m 41.8s 15m 14.8s -50.3% > Graph500 16C32T 15m 56.7s 9m 43.7s -39.0% > Pagerank 32T 1m 58.5s 1m 12.8s -38.5% > Pagerank 128T 2m 36.3s 1m 40.4s -35.7% > > Signed-off-by: Hrushikesh Salunke > Acked-by: Vlastimil Babka (SUSE) > Acked-by: Zi Yan > Acked-by: Pankaj Gupta > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David