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b=e2N/6LAiZ3lmiOQCT7v1GbceXrHi0XCDbgiPs+4M/QY/AtQXyUFVQBv6VN4/+wwnR 9VQDGaGwK3UVL+oaPqcLFD9l4X4AT7sZrQkpBhgeXSiG8a7K7CAwRz1aUAhoGeQeEm qKHVHInPdCy3tMRm59aXN7qSmn2uwxU58TpKXnJm42TH63tVOFoVa6rYwAZTkc8ZgE bJYkg1sCLmFJRaeOPKqr4+NFM1/pNlgp+4u4sPJRyiAlOnVQ/RoBH2nIxGR3z2TNfG Sf/ronQ3jqRYY4B8PIyoVSPFg7wgqO2T2PASbVCkq7fl4L1w8p96FEMReNNhOZySik 7+0vy7xtx5zQA== Message-ID: Date: Tue, 9 Jun 2026 12:14:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/slub: allocate sheaves on local memory nodes Content-Language: en-US To: Harry Yoo , Hao Li Cc: akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260601095706.106551-1-hao.li@linux.dev> <33506b25-ab2f-4f31-a380-7c0fe65567a3@kernel.org> <5d8abe93-edd1-4b18-9ea4-7731dc831223@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <5d8abe93-edd1-4b18-9ea4-7731dc831223@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: uqdhwqcwd3kyodkrkz3efzzy6nn5tppb X-Rspamd-Queue-Id: 2091E1A000D X-HE-Tag: 1781000098-451157 X-HE-Meta: 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 xndTorb4 jNVD54LzT4XvWx4islckT3+y7TeNg/KxzsDy4MKq7efKBLqDC2WpHARWI6FAj3MQtn8lZ27Wt2ja4J32FOwDCtLl2jakxUlSXshi3GPd0QFJSYfCmikfRQrtt74HJV90PGVatvio0a90fU0wqkU5bO36i3prTa/LO+XcZzCA/58yZvUnQel/PMqSYTHXFKAyLH17b1jR8mVRdGqEs/GAwK7/Zv+0dDd2Qnk44HtZXJuNC1jz1x4VHlChMzSgtzurekCwG Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/9/26 05:41, Harry Yoo wrote: > > > On 6/3/26 1:26 PM, Hao Li wrote: >> On Mon, Jun 01, 2026 at 08:28:16PM +0900, Harry Yoo wrote: >>> On 6/1/26 6:56 PM, Hao Li wrote: >>>> Sheaf structs are exchanged through node-local barns. Since barn structs >>>> are already allocated from their local NUMA node, this patch aims to >>>> allocate sheaf structs from their local memory nodes as well. >>>> >>>> To achieve this, the obvious choice would be using cpu_to_mem(). >>>> However, init_percpu_sheaves() and bootstrap_cache_sheaves() iterate >>>> through possible CPUs, whereas cpu_to_mem() is only initialized for >>>> online CPUs. Therefore, we cannot use cpu_to_mem() and instead need to >>>> use local_memory_node(cpu_to_node(cpu)), similar to what >>>> __build_all_zonelists() does. >>>> >>>> The primary goal of this patch is to improve NUMA node locality. >>>> Although the actual performance impact is minor, it still yields a ~1% >>>> improvement on a 192-core, 8-NUMA-node system when testing with the >>>> will-it-scale mmap test case. >>> >>> Oh, nice :) >>> >>> I have a question though... >>> >>> I wonder if would be better to handle this by e.g.) not returning empty >>> sheaves back to barn and freeing them if the node id doesn't match and >>> it's not a memoryless node. >>> >>> init_percpu_sheaves() and bootstrap_cache_sheaves() are not the only >>> places that can allocate sheaves from remote nodes; sheaves allocation >>> could fall back to other nodes and then SLUB could keep reusing those >>> sheaves from remote nodes even after memory is reclaimed. >> >> This is a good catch. In addition to the fallback mechanism, task migration >> between CPUs in __pcs_replace_empty_main() and __pcs_replace_full_main() can >> also mix up sheaf structs across different barns. So yeah, changing allocation >> locality is not a silver bullet. >> >>> If this works well, we probably don't need to handle it in >>> init_percpu_sheaves() and bootstrap_cache_sheaves() at all as they will >>> eventually be freed, while covering the other case too? >> >> freeing the empty sheaf if the NUMA node mismatches instead of putting it back >> into the barn is indeed a good idea. I like it. But unfortunately, my testing >> didn't show a clear performance improvement, though there was no noticeable >> degradation either. :-( > > Hmm... the idea still makes sense to me, but yeah, it's not late to fix > it when we have data to back up. I think if that approach doesn't complicate things unreasonably, it makes sense to do it even if there are no clear wins (as long as there are no regressions).