From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5BEA145560B for ; Thu, 3 Sep 2026 15:15:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788448529; cv=none; b=R0um9wxPA+Vl/TZl2QrjvSxWpLwM4SV7MlV+BTKwc40gxnrCvd3djKkSdebmxVnYMSB7ObN8zdr967TtZyylgD7QUO6rpAeDZ+lGm6bme4JlGVfTsOTonCYvhmeJUrL8pj1NekHLB4prvJ2iNynkyto2noTOk/z7YdWRKaUMKBE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788448529; c=relaxed/simple; bh=d7Kj0vaOCb2LVwyqGyIRAhDVW9Aqz/jsdCUfO2PZtPE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PT+1jo8V9r+P7Qa82yEeSIABGOLSvvF6qSgoTznXSe4TmsDu17S+GNAMP7h2Udq8qvle7afA1PgetMyK/pSHD1PzHYzwk8Wnr5N6z25ZtyYjMoFfKeK9BGpWFqfPqUrS2ZIKe40pmNubYbSK+R1M+TdJg62ZB+c6Co+O3NDDupk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ICJz8y+P; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ICJz8y+P" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52F701F000E9; Thu, 3 Sep 2026 15:15:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788448528; bh=oMud6dTUHlyEq3A7UoSwnG59ukdVv+lXzg5pPz0Fv+0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ICJz8y+PaYc9HWNIiP4kSa067DXNL5pU4EhN5COf3/xrhN9XnHBgW89lgawARDaob yXGs0djU+69lC0tsa/ziDIEehEqwopoCfSya9L+8gWIoUZH2coPsiYHUkmvcRz5rmI RA4kdB8RxyGJ27r0+rkQ4CnJRnTaGBRt8Onk4B6FGoof0ZqJCyapAlSOOCcZila6kw Em83jgfr7+3dMfaw4GvaJE6AuLhs0U5L+moC2S5jRN5JtVsoypi3kful/E3e4VwPL3 SECH8qntp7HgeeQuQls1W/SIrBqrh0yN4ygkjoRHTY4NNdg1l75mhkwwPDkVM9x3t9 UNv7To0JvsLdg== Message-ID: <906bae9d-dcf0-463b-ac9d-81ef8cc2cc2f@kernel.org> Date: Thu, 3 Sep 2026 17:15:23 +0200 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 1/2] mm: refactor find_next_best_node to find_next_best_node_in Content-Language: en-US To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com References: <20260902215853.156267-1-gourry@gourry.net> <20260902215853.156267-2-gourry@gourry.net> 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: <20260902215853.156267-2-gourry@gourry.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/2/26 23:58, Gregory Price wrote: > find_next_best_node() picks the next-closest node for a fallback list > from the full N_MEMORY set. Refactor it into find_next_best_node_in(), > which takes an explicit candidates nodemask. > > This enables building fallback lists with non-N_MEMORY candidates. > > No functional change: every caller still selects from N_MEMORY. > > Signed-off-by: Gregory Price Reviewed-by: Vlastimil Babka (SUSE) Nit: > --- > mm/internal.h | 6 ++++-- > mm/memory-tiers.c | 7 ++++--- > mm/page_alloc.c | 13 ++++++++----- > 3 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index e16f1250b25c8..18d041ff5c52c 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1130,7 +1130,8 @@ extern int node_reclaim_mode; > > extern unsigned long node_reclaim(struct pglist_data *pgdat, > gfp_t gfp_mask, unsigned int order); > -extern int find_next_best_node(int node, nodemask_t *used_node_mask); > +extern int find_next_best_node_in(int node, nodemask_t *used_node_mask, > + const nodemask_t *candidates); Drop the extern while touching a line. > #else > #define node_reclaim_mode 0 > > @@ -1139,7 +1140,8 @@ static inline unsigned long node_reclaim(struct pglist_data *pgdat, > { > return 0; > } > -static inline int find_next_best_node(int node, nodemask_t *used_node_mask) > +static inline int find_next_best_node_in(int node, nodemask_t *used_node_mask, > + const nodemask_t *candidates) > { > return NUMA_NO_NODE; > } > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c > index 54851d8a195b0..25e121851b586 100644 > --- a/mm/memory-tiers.c > +++ b/mm/memory-tiers.c > @@ -370,7 +370,7 @@ int next_demotion_node(int node, const nodemask_t *allowed_mask) > * closest demotion target. > */ > nodes_complement(mask, *allowed_mask); > - return find_next_best_node(node, &mask); > + return find_next_best_node_in(node, &mask, &node_states[N_MEMORY]); > } > > static void disable_all_demotion_targets(void) > @@ -450,7 +450,7 @@ static void establish_demotion_targets(void) > memtier = list_next_entry(memtier, list); > tier_nodes = get_memtier_nodemask(memtier); > /* > - * find_next_best_node, use 'used' nodemask as a skip list. > + * find_next_best_node_in, use 'used' nodemask as a skip list. > * Add all memory nodes except the selected memory tier > * nodelist to skip list so that we find the best node from the > * memtier nodelist. > @@ -463,7 +463,8 @@ static void establish_demotion_targets(void) > * in the preferred mask when allocating pages during demotion. > */ > do { > - target = find_next_best_node(node, &tier_nodes); > + target = find_next_best_node_in(node, &tier_nodes, > + &node_states[N_MEMORY]); > if (target == NUMA_NO_NODE) > break; > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c4dc61ec663ee..4dde1cbe2fd43 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5779,9 +5779,10 @@ static int numa_zonelist_order_handler(const struct ctl_table *table, int write, > static int node_load[MAX_NUMNODES]; > > /** > - * find_next_best_node - find the next node that should appear in a given node's fallback list > + * find_next_best_node_in - find the next node that should appear in a given node's fallback list > * @node: node whose fallback list we're appending > * @used_node_mask: nodemask_t of already used nodes > + * @candidates: nodemask_t of nodes eligible for selection > * > * We use a number of factors to determine which is the next node that should > * appear on a given node's fallback list. The node should not have appeared > @@ -5793,7 +5794,8 @@ static int node_load[MAX_NUMNODES]; > * > * Return: node id of the found node or %NUMA_NO_NODE if no node is found. > */ > -int find_next_best_node(int node, nodemask_t *used_node_mask) > +int find_next_best_node_in(int node, nodemask_t *used_node_mask, > + const nodemask_t *candidates) > { > int n, val; > int min_val = INT_MAX; > @@ -5803,12 +5805,12 @@ int find_next_best_node(int node, nodemask_t *used_node_mask) > * Use the local node if we haven't already, but for memoryless local > * node, we should skip it and fall back to other nodes. > */ > - if (!node_isset(node, *used_node_mask) && node_state(node, N_MEMORY)) { > + if (!node_isset(node, *used_node_mask) && node_isset(node, *candidates)) { > node_set(node, *used_node_mask); > return node; > } > > - for_each_node_state(n, N_MEMORY) { > + for_each_node_mask(n, *candidates) { > > /* Don't want a node to appear more than once */ > if (node_isset(n, *used_node_mask)) > @@ -5893,7 +5895,8 @@ static void build_zonelists(pg_data_t *pgdat) > prev_node = local_node; > > memset(node_order, 0, sizeof(node_order)); > - while ((node = find_next_best_node(local_node, &used_mask)) >= 0) { > + while ((node = find_next_best_node_in(local_node, &used_mask, > + &node_states[N_MEMORY])) >= 0) { > /* > * We don't want to pressure a particular node. > * So adding penalty to the first node in same