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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BL6PEPF0001AB4E.mail.protection.outlook.com (10.167.242.72) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8534.20 via Frontend Transport; Fri, 14 Mar 2025 04:18:34 +0000 Received: from [10.136.37.23] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Thu, 13 Mar 2025 23:18:03 -0500 Message-ID: <947ab5ab-3fbe-4a5c-bff5-6c257c7c5ba1@amd.com> Date: Fri, 14 Mar 2025 09:48:00 +0530 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: [RFC PATCH 7/7] sched/fair: Make sure cfs_rq has enough runtime_remaining on unthrottle path To: Aaron Lu , Valentin Schneider , Ben Segall , Peter Zijlstra , Josh Don , Ingo Molnar , Vincent Guittot CC: , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Mel Gorman , Chengming Zhou , Chuyi Zhou References: <20250313072030.1032893-1-ziqianlu@bytedance.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Mar 2025 04:18:34.6015 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f83f6af7-4853-4cbc-588f-08dd62af4960 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF0001AB4E.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8853 Hello Aaron, On 3/13/2025 12:52 PM, Aaron Lu wrote: > It's possible unthrottle_cfs_rq() is called with !runtime_remaining > due to things like user changed quota setting(see tg_set_cfs_bandwidth()) > or async unthrottled us with a positive runtime_remaining but other still > running entities consumed those runtime before we reach there. > > Anyway, we can't unthrottle this cfs_rq without any runtime remaining > because task enqueue during unthrottle can immediately trigger a throttle > by check_enqueue_throttle(), which should never happen. > > Signed-off-by: Aaron Lu > --- > kernel/sched/fair.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index be96f7d32998c..d646451d617c1 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6058,6 +6058,19 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) > struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); > struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; > > + /* > + * It's possible we are called with !runtime_remaining due to things > + * like user changed quota setting(see tg_set_cfs_bandwidth()) or async > + * unthrottled us with a positive runtime_remaining but other still > + * running entities consumed those runtime before we reach here. > + * > + * Anyway, we can't unthrottle this cfs_rq without any runtime remaining > + * because any enqueue below will immediately trigger a throttle, which > + * is not supposed to happen on unthrottle path. > + */ > + if (cfs_rq->runtime_enabled && !cfs_rq->runtime_remaining) Should this be "cfs_rq->runtime_remaining <= 0" since slack could have built up by that time we come here? > + return; > + > cfs_rq->throttled = 0; > > update_rq_clock(rq); -- Thanks and Regards, Prateek