From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (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 1542770809; Thu, 20 Aug 2026 03:33:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787196796; cv=none; b=Ii5tKQGPJCGEorZu1xMBK3RVlDYlTpqkDxuK6rl5IlNAaRlOy14JuDSSIM+Z7aLHS+EnsavyvwZIlz64PfTafMmcFg8IQbjfX/I6yoJwZv/b4b0xF6iCsMeUUpkXUczFwx4dO5d6J50bJV8wnh9jmD+i8cS+zyeq1qS/BxYeZss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787196796; c=relaxed/simple; bh=xXPbDT7vGs6wueK/VwC1fBhsuNWbYEm1hQ9WeruVY0c=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=mffgqUp/J6yXQi8cxnSh3DX56of3IyUbA0m8O8dp4+vvKOd7rMUkZ1DT/tQTFoHoTia1tQr7CuOrkCQnniTPZ4f4sXNGS7AxkEjTJKyuhwNzOHHHkYfrv8B6FAnKW2Jl5qCL/0OGvOyEdkv0dCWp6UtFE5l3ozvowNc+RAky/pM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: d7146c589c4711f19a56ed5b684f684d-20260820 X-CTIC-Tags: HR_CC_COUNT, HR_CC_DOMAIN_COUNT, HR_CC_NAME, HR_CC_NO_NAME, HR_CTE_8B HR_CTT_MISS, HR_DATE_H, HR_DATE_WKD, HR_DATE_ZONE, HR_FROM_DIGIT_LEN HR_FROM_NAME, HR_SJ_DIGIT_LEN, HR_SJ_LANG, HR_SJ_LEN, HR_SJ_LETTER HR_SJ_NOR_SYM, HR_SJ_PHRASE, HR_SJ_PHRASE_LEN, HR_SJ_WS, HR_TO_COUNT HR_TO_DOMAIN_COUNT, HR_TO_NO_NAME, IP_TRUSTED, SRC_TRUSTED, DN_TRUSTED SA_UNTRUSTED, SA_LOWREP, SA_EXISTED, SN_UNTRUSTED, SN_LOWREP SN_EXISTED, SPF_NOPASS, DKIM_NOPASS, DMARC_NOPASS, CIE_BAD CIE_GOOD, CIE_GOOD_SPF, GTI_FG_BS, GTI_RG_INFO, GTI_C_BU AMN_GOOD, ABX_MISS_RDNS X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.19,REQID:a4c6142c-1760-4e78-9667-016fa83a293a,IP:10, URL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:10 X-CID-INFO: VERSION:1.3.19,REQID:a4c6142c-1760-4e78-9667-016fa83a293a,IP:10,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION:r elease,TS:10 X-CID-META: VersionHash:7db8b62,CLOUDID:b5620d622c810dd47606d8ed7488c307,BulkI D:2608201128202I10ZPYF,BulkQuantity:1,SF:17|19|38|66|78|81|82|102|127|136| 850|865|898,TC:nil,Content:0|15|50,EDM:-3|-100,IP:-2,URL:0,File:nil,RT:nil ,Bulk:40,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BR R:0,BRE:0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_FAS,TF_CID_SPAM_FSD X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: d7146c589c4711f19a56ed5b684f684d-20260820 X-User: liuzhe1@kylinos.cn Received: from localhost.localdomain [(223.70.159.239)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 2037768217; Thu, 20 Aug 2026 11:32:59 +0800 From: Zhe Liu To: tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, corbet@lwn.net, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: skhan@linuxfoundation.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Zhe Liu Subject: [PATCH 2/2] Documentation: describe burst reset on quota changes Date: Thu, 20 Aug 2026 11:32:18 +0800 Message-Id: <20260820033218.214259-3-liuzhe1@kylinos.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260820033218.214259-1-liuzhe1@kylinos.cn> References: <20260820033218.214259-1-liuzhe1@kylinos.cn> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Document that an incompatible burst is reset when a finite quota is written through the cgroup v1 or cgroup v2 CPU bandwidth interface, while compatible bursts and unlimited quota updates preserve the existing value. Signed-off-by: Zhe Liu --- Documentation/admin-guide/cgroup-v2.rst | 5 ++++- Documentation/scheduler/sched-bwc.rst | 14 ++++++++------ 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index aed195a71cbf..9f5e43d96476 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1200,7 +1200,10 @@ will be referred to. All time durations are in microseconds. which indicates that the group may consume up to $MAX in each $PERIOD duration. "max" for $MAX indicates no limit. If only - one number is written, $MAX is updated. + one number is written, $MAX is updated. When a finite $MAX is + written, an existing cpu.max.burst value which is incompatible + with the new limit is reset to zero. Writing "max" leaves the + burst value unchanged. This file affects only processes under the fair-class scheduler. diff --git a/Documentation/scheduler/sched-bwc.rst b/Documentation/scheduler/sched-bwc.rst index e881a945c188..79bd5f254e50 100644 --- a/Documentation/scheduler/sched-bwc.rst +++ b/Documentation/scheduler/sched-bwc.rst @@ -90,14 +90,16 @@ bandwidth restriction in place, such a group is described as an unconstrained bandwidth group. This represents the traditional work-conserving behavior for CFS. -Writing any (valid) positive value(s) no smaller than cpu.cfs_burst_us will -enact the specified bandwidth limit. The minimum quota allowed for the quota or -period is 1ms. There is also an upper bound on the period length of 1s. -Additional restrictions exist when bandwidth limits are used in a hierarchical -fashion, these are explained in more detail below. +Writing any valid positive value will enact the specified bandwidth limit. If +the existing cpu.cfs_burst_us value is incompatible with the new quota, it is +reset to zero. The minimum quota allowed for the quota or period is 1ms. There +is also an upper bound on the period length of 1s. Additional restrictions +exist when bandwidth limits are used in a hierarchical fashion, these are +explained in more detail below. Writing any negative value to cpu.cfs_quota_us will remove the bandwidth limit -and return the group to an unconstrained state once more. +and return the group to an unconstrained state once more. The existing +cpu.cfs_burst_us value remains unchanged. A value of 0 for cpu.cfs_burst_us indicates that the group can not accumulate any unused bandwidth. It makes the traditional bandwidth control behavior for -- 2.25.1