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([2601:188:c102:b180:1f8b:71d0:77b1:1f6e]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-944122ae554sm23610471241.2.2026.01.14.14.33.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Jan 2026 14:33:17 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <51675d7c-5c9d-4596-8e5c-692c90b79e06@redhat.com> Date: Wed, 14 Jan 2026 17:33:06 -0500 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 3/3] cgroup: use nodes_and() output where appropriate To: Yury Norov , Andrew Morton , Alistair Popple , Byungchul Park , David Hildenbrand , Gregory Price , Johannes Weiner , Joshua Hahn , "Liam R. Howlett" , Lorenzo Stoakes , Matthew Brost , Michal Hocko , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Mike Rapoport , Rakie Kim , Suren Baghdasaryan , Tejun Heo , Vlastimil Babka , Ying Huang , Zi Yan , cgroups@vger.kernel.org Cc: Yury Norov , Rasmus Villemoes , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260114172217.861204-1-ynorov@nvidia.com> <20260114172217.861204-4-ynorov@nvidia.com> Content-Language: en-US In-Reply-To: <20260114172217.861204-4-ynorov@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/14/26 12:22 PM, Yury Norov wrote: > Now that nodes_and() returns true if the result nodemask is not empty, > drop useless nodes_intersects() in guarantee_online_mems() and > nodes_empty() in update_nodemasks_hier(), which both are O(N). > > Signed-off-by: Yury Norov > --- > kernel/cgroup/cpuset.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 3e8cc34d8d50..e962efbb300d 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -456,9 +456,8 @@ static void guarantee_active_cpus(struct task_struct *tsk, > */ > static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask) > { > - while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY])) > + while (!nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY])) > cs = parent_cs(cs); > - nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]); > } > > /** > @@ -2862,13 +2861,13 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) > cpuset_for_each_descendant_pre(cp, pos_css, cs) { > struct cpuset *parent = parent_cs(cp); > > - nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems); > + bool has_mems = nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems); > > /* > * If it becomes empty, inherit the effective mask of the > * parent, which is guaranteed to have some MEMs. > */ > - if (is_in_v2_mode() && nodes_empty(*new_mems)) > + if (is_in_v2_mode() && !has_mems) > *new_mems = parent->effective_mems; > > /* Skip the whole subtree if the nodemask remains the same. */ Reviewed-by: Waiman Long