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Fri, 16 Feb 2024 13:50:22 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id COudIh5oz2WJMAAAn2gu4w (envelope-from ); Fri, 16 Feb 2024 13:50:22 +0000 Date: Fri, 16 Feb 2024 14:51:24 +0100 From: Oscar Salvador To: Byungchul Park Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org Subject: Re: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY Message-ID: References: <20240216114045.24828-1-byungchul@sk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240216114045.24828-1-byungchul@sk.com> X-Rspamd-Queue-Id: 4B25A12000A X-Rspam-User: X-Stat-Signature: 8wp79oewwcp15noqncyibbjzccn7hteq X-Rspamd-Server: rspam03 X-HE-Tag: 1708091427-325822 X-HE-Meta: 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 YjJ4zHyA FBDowNeq74bqPFz4VS5Ent156Oz0h0/M9aZP1NvMr/J4oB/X8Olgf+L4g2GhUWgln5bd2R9IDbL6BBXy7gdbhEf/XsFx87x/zyhOKfy3C+BmeSn4LgChAtvAPQbCSrsxHaaor2beuLI2txsWs3OX3W1Nw79q5Hc9C7++C8/zFQCggsmuiRWjjwmopbvXnb7vpXqrXHnhtjA+mAsObz2i37YnnT5Sd2gwR6UJNdTJi/zm6cHgjiUcpEIzL2dYkJBhbGtA3ey+JJNelff2VxFoGndpptUb28RzJy71lGPoYKrPuYfcji5nuFpLuJA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 16, 2024 at 08:40:45PM +0900, Byungchul Park wrote: > From 150af2f78e19217a1d03e47e3ee5279684590fb4 Mon Sep 17 00:00:00 2001 > From: Byungchul Park > Date: Fri, 16 Feb 2024 20:18:10 +0900 > Subject: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY "do not try to promote folios to memoryless nodes" because AFAICS we are just trying. Even if should_numa_migrate_memory() returns true, I assume that we will fail somewhere down the chain e.g: migrate_pages() when we see that this node does not any memory, right? > A numa node might not have its local memory but CPUs. Promoting a folio > to the node's local memory is nonsense. So avoid nodes not set N_MEMORY > from getting promoted. If you talk about memoryless nodes everybody gets it better IMHO. "Memoryless nodes do not have any memory to migrate to, so stop trying it." > Signed-off-by: Byungchul Park > --- > kernel/sched/fair.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index d7a3c63a2171..7ed9ef3c0134 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1828,6 +1828,13 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, > int dst_nid = cpu_to_node(dst_cpu); > int last_cpupid, this_cpupid; > > + /* > + * A node of dst_nid might not have its local memory. Promoting > + * a folio to the node is meaningless. > + */ > + if (!node_state(dst_nid, N_MEMORY)) > + return false; "Cannot migrate to memoryless nodes" seems shorter and more clear. So, what happens when we return true here? will we fail at migrate_pages() I guess? That is quite down the road so I guess this check can save us some time. -- Oscar Salvador SUSE Labs