From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CCF15CDB470 for ; Mon, 22 Jun 2026 12:31:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A6B576B0088; Mon, 22 Jun 2026 08:31:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A1C396B008A; Mon, 22 Jun 2026 08:31:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8E4D06B008C; Mon, 22 Jun 2026 08:31:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 6204F6B0088 for ; Mon, 22 Jun 2026 08:31:46 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E5A031C01FE for ; Mon, 22 Jun 2026 12:31:45 +0000 (UTC) X-FDA: 84907484970.21.FB4F908 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf06.hostedemail.com (Postfix) with ESMTP id 29C6C180003 for ; Mon, 22 Jun 2026 12:31:44 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Yq6Bpl9x; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782131504; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=mv1TDIjJmBLfFfHDh7TWc3Ec+yFIfWNb9f4z3gl0gSU=; b=AGysRyyfjzNA4smAajl2d9IO8+sLpOy76Ll/dq8RfHdBCifA2a2NwCCbFCeCzDKiYd9OpT vAUOAqeEUGIzxZe9DlK9BwcCLzQz9W6/DXoNJ3+vYhyYHOibVDhojE+7MFKPelXXyBUz9I 9AaERvFZOksdvJoMOJjf8T4ILram6kc= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782131504; b=auKg7EAqgrjigwWm2joTx+iGr/cMYAv3rIDxNMClVtpXBBXYopqEnYVefksKswvQ5xNcQE X1bjKvggOhAcX/PmPo28w5Xm8gza9Y9lI36qHPjjf6mSLXAWVL+vBh4JaxK+ArCQp3wu9l rKTlEe7QlxUrs4zHhOMKTJgySyX3HWQ= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Yq6Bpl9x; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5FD806008A; Mon, 22 Jun 2026 12:31:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E0ED1F000E9; Mon, 22 Jun 2026 12:31:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782131503; bh=mv1TDIjJmBLfFfHDh7TWc3Ec+yFIfWNb9f4z3gl0gSU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Yq6Bpl9xNgG8eaRATgdPo0E6+dJzOGDQdCno3iqmf9KIjIyllG26382Fr+fu01Xf9 bUxEbSPKJ8PlEknLGKhUqgRA61PAmFzSJyc1PboFoovpAJAw/XooS3FS6ehllQovLR lZjaUXJqM2NijaocEgvjjV0L0wYR640roDVz94qNQodlQ/fWv/DAdDjodvjLDklrZs 5/kg/o5GRcSCI3UnWdBn5hE0/Yxen3qdzKU4Pv1QmF/0aj1G+OQ+VuKGt8hcVDMbXm 6CrJEankWsCzYKYacNiCs0vkPokNkFSC7JFUDLoURnu1O0TSFTiyMNn3+RaT36bGsh H6c0z304WZg0A== Message-ID: <6b22698c-ac2e-4c71-9448-50f073b4efc6@kernel.org> Date: Mon, 22 Jun 2026 14:31:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) Content-Language: en-US To: Gregory Price Cc: "David Hildenbrand (Arm)" , Balbir Singh , lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, longman@redhat.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com, Matthew Wilcox References: <9f1815b0-896b-44ab-9e6d-9316d8f11033@kernel.org> <90418cd3-751f-439d-83ed-a0c33517c3bd@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Stat-Signature: cmx4hseubjezgg5smfqzm8o9i5fad5ii X-Rspamd-Queue-Id: 29C6C180003 X-Rspam-User: X-HE-Tag: 1782131504-639873 X-HE-Meta: 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 LgPl8oXg UXMP/FkEstk0FUxjqF32FYzHh1eBrfBW9u10VpRgwGmROL5NBl1XkyoKnTaIRY2Qb6O/VHIq3OivGZSWFX3aOVKnkTF9GgVVqItc1OT8eMGWqkeA+ZiWlGulYGK0gfGZX3ydIpxh7wU/b8zzEI2e5uyDRHTsQmsP9nxXs2W2184AEGSDi0pN0LjjePtEUrSXdlNjW6biWYQunxKcCECvRh8sFsFuLIUJMwno293OSaTKxD26DX8BdoCe4Ar0IBJcCL+Hr6G/YJLAm5xsnQAYpltV1QC8s9N52DY8osULRo11mQLQlCPN8p1u4ZICENDAG6MhZuKPrLDjtW9w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/18/26 13:13, Gregory Price wrote: > On Thu, Jun 18, 2026 at 10:21:30AM +0200, Vlastimil Babka (SUSE) wrote: >> On 6/15/26 17:37, Gregory Price wrote: >> > >> > One thought would be a way to switch what fallback list is used, and >> > then have specific fallback lists for certain contexts. >> > >> > Right now there is a single example of this: __GFP_THISNODE >> > |= __GFP_THISNODE => NOFALLBACK >> > &= ~__GFP_THISNODE => FALLBACK >> > >> > We could add an interface with the desired fallback list based as an >> > argument, and let get_page_from_freelist to prefer that over the default >> > global lists. >> >> Does it mean a new argument in a number of functions in the page allocator, >> or can it be mapped to alloc_flags (at least internally?), because the >> number of possible fallback lists is small enough? >> > > What I ended up with was adding a single page_alloc.c external interface > that allows you define the zonelist via an enum, and then an internal > selector resolution in prepare_alloc_pages() stored in alloc_context OK. Since it's in alloc_context then there should be no parameter bloat inside page allocator. And for the single external entry point it's better to be explicit. > > eg: > > static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order, > int preferred_nid, nodemask_t *nodemask, > struct alloc_context *ac, gfp_t *alloc_gfp, > unsigned int *alloc_flags) > { > ac->highest_zoneidx = gfp_zone(gfp_mask); > ac->zonelist = select_zonelist(preferred_nid, gfp_mask, ac->zlsel); > ... snip ... > } > > struct folio *__folio_alloc_zonelist_noprof(gfp_t gfp, unsigned int order, > int preferred_nid, nodemask_t *nodemask, > enum alloc_zonelist zlsel); > > > The original __folio_alloc* functions just add a DEFAULT - which tells > select_zonelist() to base the decision on __GFP_THISNODE. > > > struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid, > nodemask_t *nodemask) > { > return __folio_alloc_core(gfp, order, preferred_nid, nodemask, > ALLOC_ZONELIST_DEFAULT); > } > EXPORT_SYMBOL(__folio_alloc_noprof); > > > This does a few things > - The isolation is structural, there is no way to accidentally > allocate private memory without passing ALLOC_ZONELIST_PRIVATE > > - The isolation forces folios - there are no non-folio interfaces > which allow zonelist selection > > - The zonelist selection is confined to this allocation context, > so no inheritence is possible. > Ack. > > I tried to avoid using an ALLOC_ flag so we can avoid yet another flag > crunch, but there certainly are few enough zonelists that we could > encode it there and expose it. I know Brendan was looking at plumbing > alloc flags out to an interface, so i'm open to that. > > Externally the way I determine what zonelist to use is a lookup based on > reason - letting the node filter. This is really only needed in a > couple spots: > > mm/khugepaged.c: enum alloc_zonelist zlsel = alloc_zonelist_for_node(node, NODE_ALLOC_RECLAIM); > mm/vmscan.c: mtc->zlsel = alloc_zonelist_for_nodemask(mtc->nmask, NODE_ALLOC_TIERING); > mm/migrate.c: .zlsel = alloc_zonelist_for_node(node, NODE_ALLOC_USER_MIGRATE), > > static inline enum alloc_zonelist > alloc_zonelist_for_node(int nid, enum node_alloc_reason reason) > { > bool ok; > > if (!node_state(nid, N_MEMORY_PRIVATE)) > return ALLOC_ZONELIST_DEFAULT; > switch (reason) { > case NODE_ALLOC_RECLAIM: > ok = node_is_reclaimable(nid); > break; > case NODE_ALLOC_TIERING: > ok = node_allows_tiering(nid); > break; > case NODE_ALLOC_USER_MIGRATE: > ok = node_allows_user_migrate(nid); > break; > default: > ok = false; > } > return ok ? ALLOC_ZONELIST_PRIVATE : ALLOC_ZONELIST_DEFAULT; > } > > Otherwise... everything is now a mempolicy w/ MPOL_F_BIND and all the > handling goes through the normal fault-paths :] > > static struct page *__alloc_pages_mpol(gfp_t gfp, unsigned int order, > struct mempolicy *pol, pgoff_t ilx, int nid) > { > nodemask_t *nodemask; > struct page *page; > enum alloc_zonelist zlsel = (pol->flags & MPOL_F_PRIVATE) ? > ALLOC_ZONELIST_PRIVATE : ALLOC_ZONELIST_DEFAULT; > ... > if (pol->mode == MPOL_PREFERRED_MANY) > return alloc_pages_preferred_many(gfp, order, nid, nodemask, > zlsel); > ... > } > > > Switching to an alloc_flag would probably be trivially if that's really > wanted I guess not. Thanks for the explanation! > ~Gregory