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Thu, 18 Dec 2025 10:11:56 +0000 (GMT) Message-ID: <6f0954ba-2ca7-41e8-b4f7-b0b17990f659@linux.ibm.com> Date: Thu, 18 Dec 2025 15:41:55 +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: [tip:sched/core] [sched/fair] 089d84203a: pts.schbench.32.usec,_99.9th_latency_percentile 52.4% regression To: Peter Zijlstra , kernel test robot Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar , Linus Torvalds , Dietmar Eggemann , Juri Lelli , Mel Gorman , Valentin Schneider , Vincent Guittot , aubrey.li@linux.intel.com, yu.c.chen@intel.com References: <202512181208.753b9f6e-lkp@intel.com> <20251218083747.GI3707891@noisy.programming.kicks-ass.net> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20251218083747.GI3707891@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjEzMDAxOCBTYWx0ZWRfXwQLzewxi9rpD 2rUYkDiZRQNw+zZWA8ADeLVhX297KuJWJKPuOe9nK/16ksZuCOTTpsRrpSOmK5PwhMKAgnxGGjr gdANyuylNDZ/+MGbQqnc4wMAk5XUKv6NZcka/Xx/HVSoZeT4DwTQhxHoZUSr1OjHDDEaEoADw77 n5maQ16jDSyKvrbgbhuLEWkFviZhWno5V6Wutgvom8RA1eVjDeL2dD3eS3m7RuHqhpk5InCyIQn cbFT8jklMRWGCOuUJjyM9SJLKe9tZdQE/pAfr6RanTvx1+7SRZhyIDXEeN9tw7SafaENfHOM6+S RmXJ0v+tub+gsMx1JwbEV2E7ek8xthvnWmdO0yVXC8F9NXImifUfd11noPp4NPFGov8mRhGP1Jv qUDgMaid6jxUf4R0RfhCTik7NLlz/g== X-Proofpoint-GUID: Aat6kv_jpeoMQ27UkXs-QR_Iev-WEn-S X-Proofpoint-ORIG-GUID: Aat6kv_jpeoMQ27UkXs-QR_Iev-WEn-S X-Authority-Analysis: v=2.4 cv=LbYxKzfi c=1 sm=1 tr=0 ts=6943d372 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=AAfG2KVKSz7IoxDedYMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-18_01,2025-12-17_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 phishscore=0 clxscore=1011 suspectscore=0 adultscore=0 malwarescore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2512130018 On 12/18/25 2:07 PM, Peter Zijlstra wrote: > On Thu, Dec 18, 2025 at 12:59:53PM +0800, kernel test robot wrote: >> >> >> Hello, >> >> kernel test robot noticed a 52.4% regression of pts.schbench.32.usec,_99.9th_latency_percentile on: >> >> >> commit: 089d84203ad42bc8fd6dbf41683e162ac6e848cd ("sched/fair: Fold the sched_avg update") >> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git sched/core > > Well, that obviously wasn't the intention. Let me pull that patch :/ Is it possible because it missed scaling by se_weight(se) ?? +#define __update_sa(sa, name, delta_avg, delta_sum) do { \ + add_positive(&(sa)->name##_avg, delta_avg); \ + add_positive(&(sa)->name##_sum, delta_sum); \ + (sa)->name##_sum = max_t(typeof((sa)->name##_sum), \ + (sa)->name##_sum, \ + (sa)->name##_avg * PELT_MIN_DIVIDER); \ +} while (0) + static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { - cfs_rq->avg.load_avg += se->avg.load_avg; - cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum; + __update_sa(&cfs_rq->avg, load, se->avg.load_avg, se->avg.load_sum); }