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b=I3SeDa5y8FjLpHVH3jLFvHwdKcD3Y8ondN5UxOmGWi9uVCNqL/eELQoSgA+VxYHvp wegZn2RAKvkr3iTkwjPZzAWvUMZgXWSUIsyfl66fOw7SmB8BeeNgxOzJIVrlhr6UCK Ke7x76llpRjY3DSgmwY8jSynKJ+YqiummrJmjHyk3vSY0aTRGrCdvHszKU3bk+e/T2 oldt6cKBjO4Y0ZLcW9G5g2go+1nuBJEWN78bHPsDPWk75edEbdLR4vMZsnFPlttmEL 3LvStkS7YILFS90rKMwwQw3JLQMaMeBtQn9iin1gQ+a+z2lV+xNbTuSQtizadK/bbp MY9oFNPNu1Wgw== Message-ID: <9f67cacc-b063-48b7-81af-09858aa5dcdb@kernel.org> Date: Thu, 3 Sep 2026 17:33:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/page_alloc: refactor build_node_zonelist() out of build_zonelists() 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> <20260902215853.156267-3-gourry@gourry.net> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 574AD2000A X-Stat-Signature: 1k1dprds4nwseqfgmjicuyz64b89biaa X-HE-Tag: 1788449627-326579 X-HE-Meta: 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 QQlhCrY6 6L1KVreqlLkmeE3H3OtUl4TM70W2APgOtSDiF27aWYeoSunXfHhcURejVEeYZwVGC/cjhkEKgdRk8CpBYyhT4+jUIzWq6U2LW7kd57rQjGBqkoQ9ZdEyperJaK70oaxKHJj5Gz+w7aCW/+MD0/gXglc0RBnnkr+pBjqDWPcKWAKgF5tcKgrKU/yPtxe1/Oqo/x5dFwhtt+vHmtOxN8EblfSqWSipIWH4+jwaaC1mDfb6iVFiPp3X5YxNFnM4E8U7W6M4zRfogREZYL3aM/2q9tladCykJcVoQEI18lYm36/i+YK16Va8W+qX6/g5SCDKc4QQ+BoTApNmn4eUGNw1MVZ9Ib3bR4+4F5/KPX5oRhLQje4E= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/2/26 23:58, Gregory Price wrote: > Extract per-node fallback-list construction into build_node_zonelist(). > > This lets us build new zonelists from candidate nodemasks instead of > just the default N_MEMORY node state list. > > No functional change: build_zonelists() builds the same FALLBACK list over > N_MEMORY with node_load updates as before. > > Signed-off-by: Gregory Price LGTM, but, while we're at it, could we just do the pr_cont() printing in build_node_zonelist() itself (maybe behind a flag if you don't want to print from future new caller) so it doesn't need to pass nr_nodes back to build_zonelists(). Then also the node_order array could live in build_node_zonelist() itself? Actually I wonder if we could get ride of the node_order array completely. It would mean the loop processing in build_zonelists_in_node_order() would have to be done piece-meal in build_node_zonelist() itself. But seems feasible? Depends on how you intend to reuse/extend the new functions later, I guess... > --- > mm/page_alloc.c | 44 ++++++++++++++++++++++++++++++-------------- > 1 file changed, 30 insertions(+), 14 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 4dde1cbe2fd43..e1d7c8b221d0d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5849,12 +5849,12 @@ int find_next_best_node_in(int node, nodemask_t *used_node_mask, > * DMA zone, if any--but risks exhausting DMA zone. > */ > static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order, > - unsigned nr_nodes) > + unsigned int nr_nodes, int zlidx) > { > struct zoneref *zonerefs; > int i; > > - zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs; > + zonerefs = pgdat->node_zonelists[zlidx]._zonerefs; > > for (i = 0; i < nr_nodes; i++) { > int nr_zones; > @@ -5883,26 +5883,28 @@ static void build_thisnode_zonelists(pg_data_t *pgdat) > zonerefs->zone_idx = 0; > } > > -static void build_zonelists(pg_data_t *pgdat) > +/* > + * Build one node-ordered fallback list from a candidate nodemask. > + * update_load round-robins node_load across equidistant nodes. > + */ > +static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates, > + int zlidx, bool update_load, > + int *node_order, int *nr) > { > - static int node_order[MAX_NUMNODES]; > - int node, nr_nodes = 0; > nodemask_t used_mask = NODE_MASK_NONE; > - int local_node, prev_node; > - > - /* NUMA-aware ordering of nodes */ > - local_node = pgdat->node_id; > - prev_node = local_node; > + int local_node = pgdat->node_id; > + int prev_node = local_node; > + int node, nr_nodes = 0; > > - memset(node_order, 0, sizeof(node_order)); > while ((node = find_next_best_node_in(local_node, &used_mask, > - &node_states[N_MEMORY])) >= 0) { > + candidates)) >= 0) { > /* > * We don't want to pressure a particular node. > * So adding penalty to the first node in same > * distance group to make it round-robin. > */ > - if (node_distance(local_node, node) != > + if (update_load && > + node_distance(local_node, node) != > node_distance(local_node, prev_node)) > node_load[node] += 1; > > @@ -5910,8 +5912,22 @@ static void build_zonelists(pg_data_t *pgdat) > prev_node = node; > } > > - build_zonelists_in_node_order(pgdat, node_order, nr_nodes); > + build_zonelists_in_node_order(pgdat, node_order, nr_nodes, zlidx); > + *nr = nr_nodes; > +} > + > +static void build_zonelists(pg_data_t *pgdat) > +{ > + static int node_order[MAX_NUMNODES]; > + int local_node = pgdat->node_id; > + int node, nr_nodes = 0; > + > + memset(node_order, 0, sizeof(node_order)); > + > + build_node_zonelist(pgdat, &node_states[N_MEMORY], ZONELIST_FALLBACK, > + true, node_order, &nr_nodes); > build_thisnode_zonelists(pgdat); > + > pr_info("Fallback order for Node %d: ", local_node); > for (node = 0; node < nr_nodes; node++) > pr_cont("%d ", node_order[node]);