From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 ABBDD2D877B; Mon, 17 Nov 2025 07:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763365555; cv=none; b=EJWzYmYzbYZs805qvsUrE+iqM6AKuEVfQOEKAv18esUPh1cCOoUcHyifMHwJFCOY/jfC8Er1YnOTZb5BmQzP/CjZJvTKZofHcC1TPFT+6C8qnZF6mQrkp7uK3MfAFoKoT7UXU4fBR74l6T6pVIeBUfjxUFhlyJxttm/h6+h3SmE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763365555; c=relaxed/simple; bh=EbNxfSdIJxkkYRxf8iJ7gn0LKWwTw9Xv1/OhMGTP6rQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=l5UfuHc6uTPsNzOEWdNAD8Wck+ezzOf567dRht0mB0SBiFb92SoagMknBOnDgySOjbgUykyw8JF/5S5FhsukOysVq4A+e7wq15O0RlGrYTiQnb64LHPFWmaU6xwsZWdKduv1MUoYNLvAEBeRK0+QPs6pvfxu/A6k4Bht9OB4z3k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4d90CD43ZYzYQv57; Mon, 17 Nov 2025 15:45:12 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 0A2431A1A48; Mon, 17 Nov 2025 15:45:49 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP4 (Coremail) with SMTP id gCh0CgBnj1yr0hppanUoBA--.12700S2; Mon, 17 Nov 2025 15:45:48 +0800 (CST) Message-ID: Date: Mon, 17 Nov 2025 15:45:47 +0800 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 v4 1/1] cpuset: relax the overlap check for cgroup-v2 To: Sun Shaojie , llong@redhat.com Cc: mkoutny@suse.com, cgroups@vger.kernel.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, shuah@kernel.org, tj@kernel.org References: <20251117015708.977585-1-sunshaojie@kylinos.cn> <20251117015708.977585-2-sunshaojie@kylinos.cn> Content-Language: en-US From: Chen Ridong In-Reply-To: <20251117015708.977585-2-sunshaojie@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CM-TRANSID:gCh0CgBnj1yr0hppanUoBA--.12700S2 X-Coremail-Antispam: 1UD129KBjvJXoW3Ar15CFWUCw4rCF4rKFyUKFg_yoW3uF48pF W8GF4jy3yjgF1UCw13Kr1kWrsYgw40qFnrtrn5Jr1rAF9rJF1xArn8JwnxtFy5XrZ8Ww13 ZFZIy3yfuFs8trUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyCb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxkF7I0En4kS14v26r1q6r43MxAIw28IcxkI7VAK I48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7 xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xII jxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw2 0EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x02 67AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZFpf9x07UAwIDUUUUU= X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ On 2025/11/17 9:57, Sun Shaojie wrote: > In cgroup v2, a mutual overlap check is required when at least one of two > cpusets is exclusive. However, this check should be relaxed and limited to > cases where both cpusets are exclusive. > > This patch ensures that for sibling cpusets A1 (exclusive) and B1 > (non-exclusive), change B1 cannot affect A1's exclusivity. > > for example. Assume a machine has 4 CPUs (0-3). > > root cgroup > / \ > A1 B1 > > Case 1: > Table 1.1: Before applying the patch > Step | A1's prstate | B1'sprstate | > #1> echo "0-1" > A1/cpuset.cpus | member | member | > #2> echo "root" > A1/cpuset.cpus.partition | root | member | > #3> echo "0" > B1/cpuset.cpus | root invalid | member | > > After step #3, A1 changes from "root" to "root invalid" because its CPUs > (0-1) overlap with those requested by B1 (0-3). However, B1 can actually B1 (0-3) --> B1(0) ? > use CPUs 2-3(from B1's parent), so it would be more reasonable for A1 to > remain as "root." > > Table 1.2: After applying the patch > Step | A1's prstate | B1'sprstate | > #1> echo "0-1" > A1/cpuset.cpus | member | member | > #2> echo "root" > A1/cpuset.cpus.partition | root | member | > #3> echo "0" > B1/cpuset.cpus | root | member | > > All other cases remain unaffected. For example, cgroup-v1, both A1 and B1 > are exclusive or non-exlusive. > > Signed-off-by: Sun Shaojie > --- > kernel/cgroup/cpuset-internal.h | 3 ++ > kernel/cgroup/cpuset-v1.c | 20 +++++++++ > kernel/cgroup/cpuset.c | 43 ++++++++++++++----- > .../selftests/cgroup/test_cpuset_prs.sh | 5 ++- > 4 files changed, 58 insertions(+), 13 deletions(-) > > diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h > index 337608f408ce..c53111998432 100644 > --- a/kernel/cgroup/cpuset-internal.h > +++ b/kernel/cgroup/cpuset-internal.h > @@ -292,6 +292,7 @@ void cpuset1_hotplug_update_tasks(struct cpuset *cs, > struct cpumask *new_cpus, nodemask_t *new_mems, > bool cpus_updated, bool mems_updated); > int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial); > +bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2); > #else > static inline void fmeter_init(struct fmeter *fmp) {} > static inline void cpuset1_update_task_spread_flags(struct cpuset *cs, > @@ -302,6 +303,8 @@ static inline void cpuset1_hotplug_update_tasks(struct cpuset *cs, > bool cpus_updated, bool mems_updated) {} > static inline int cpuset1_validate_change(struct cpuset *cur, > struct cpuset *trial) { return 0; } > +static inline bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, > + struct cpuset *cs2) {return false; } > #endif /* CONFIG_CPUSETS_V1 */ > > #endif /* __CPUSET_INTERNAL_H */ > diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c > index 12e76774c75b..5c1296bf6a34 100644 > --- a/kernel/cgroup/cpuset-v1.c > +++ b/kernel/cgroup/cpuset-v1.c > @@ -373,6 +373,26 @@ int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial) > return ret; > } > > +/* > + * cpuset1_cpus_excl_conflict() - Check if two cpusets have exclusive CPU conflicts > + * to legacy (v1) > + * @cs1: first cpuset to check > + * @cs2: second cpuset to check > + * > + * Returns: true if CPU exclusivity conflict exists, false otherwise > + * > + * If either cpuset is CPU exclusive, their allowed CPUs cannot intersect. > + */ > +bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) > +{ > + if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2)) > + if (cpumask_intersects(cs1->cpus_allowed, > + cs2->cpus_allowed)) > + return true; > + > + return false; > +} > + > #ifdef CONFIG_PROC_PID_CPUSET > /* > * proc_cpuset_show() > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 52468d2c178a..0fd803612513 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -580,35 +580,56 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2) > > /** > * cpus_excl_conflict - Check if two cpusets have exclusive CPU conflicts > - * @cs1: first cpuset to check > - * @cs2: second cpuset to check > + * @cs1: current cpuset to check > + * @cs2: cpuset involved in the check > * > * Returns: true if CPU exclusivity conflict exists, false otherwise > * > * Conflict detection rules: > - * 1. If either cpuset is CPU exclusive, they must be mutually exclusive > + * For cgroup-v1: > + * see cpuset1_cpus_excl_conflict() > + * For cgroup-v2: > + * 1. If cs1 is exclusive, cs1 and cs2 must be mutually exclusive > * 2. exclusive_cpus masks cannot intersect between cpusets > - * 3. The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs > + * 3. If cs2 is exclusive, cs2's allowed CPUs cannot be a subset of cs1's exclusive CPUs > + * 4. if cs1 and cs2 are not exclusive, the allowed CPUs of one cpuset cannot be a subset > + * of another's exclusive CPUs > */ The revised conflict detection rules are confusing to me. I thought cs1 and cs2 should be treated symmetrically, but that doesn’t seem to be the case here. Shouldn’t the following rule apply regardless of whether cs1 or cs2 is exclusive: "The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs"? > static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) > { > - /* If either cpuset is exclusive, check if they are mutually exclusive */ > - if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2)) > + /* For cgroup-v1 */ > + if (!cpuset_v2()) > + return cpuset1_cpus_excl_conflict(cs1, cs2); > + > + /* If cs1 are exclusive, check if they are mutually exclusive */ > + if (is_cpu_exclusive(cs1)) > return !cpusets_are_exclusive(cs1, cs2); > > + /* The following check applies when either > + * both cs1 and cs2 are non-exclusive，or > + * only cs2 is exclusive. > + */ > + > /* Exclusive_cpus cannot intersect */ > if (cpumask_intersects(cs1->exclusive_cpus, cs2->exclusive_cpus)) > return true; > > - /* The cpus_allowed of one cpuset cannot be a subset of another cpuset's exclusive_cpus */ > - if (!cpumask_empty(cs1->cpus_allowed) && > - cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus)) > - return true; > - > + /* cs2's allowed CPUs cannot be a subset of cs1's exclusive CPUs */ > if (!cpumask_empty(cs2->cpus_allowed) && > cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus)) > return true; > > + /* If cs2 is exclusive, check finished here */ > + if (is_cpu_exclusive(cs2)) > + return false; > + > + /* The following check applies only if both cs1 and cs2 are non-exclusive. */ > + > + /* cs1's allowed CPUs cannot be a subset of cs1's exclusive CPUs */ > + if (!cpumask_empty(cs1->cpus_allowed) && > + cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus)) > + return true; > + > return false; > } > >From your commit message, it appears you intend to modify "if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))" to "if (is_cpu_exclusive(cs1) && is_cpu_exclusive(cs2))". However, I’m having trouble following the change. > diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh > index a17256d9f88a..b848bc0729cf 100755 > --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh > +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh > @@ -388,10 +388,11 @@ TEST_MATRIX=( > " C0-1:S+ C1 . C2-3 . P2 . . 0 A1:0-1|A2:1 A1:P0|A2:P-2" > " C0-1:S+ C1:P2 . C2-3 P1 . . . 0 A1:0|A2:1 A1:P1|A2:P2 0-1|1" > > - # A non-exclusive cpuset.cpus change will invalidate partition and its siblings > + # A non-exclusive cpuset.cpus change will not invalidate its siblings partition. > + # But a exclusive cpuset.cpus change will invalidate itself. > " C0-1:P1 . . C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P0" > " C0-1:P1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P-1" > - " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P0|B1:P-1" > + " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-1|B1:2-3 A1:P0|B1:P1" > > # cpuset.cpus can overlap with sibling cpuset.cpus.exclusive but not subsumed by it > " C0-3 . . C4-5 X5 . . . 0 A1:0-3|B1:4-5" -- Best regards, Ridong