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Thu, 10 Jul 2025 07:00:05 GMT Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EE22758063; Thu, 10 Jul 2025 07:00:04 +0000 (GMT) Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EF3E158065; Thu, 10 Jul 2025 07:00:00 +0000 (GMT) Received: from [9.204.206.228] (unknown [9.204.206.228]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 10 Jul 2025 07:00:00 +0000 (GMT) Message-ID: <5bbe61ee-d384-47b9-b6f2-c9f607f00156@linux.ibm.com> Date: Thu, 10 Jul 2025 12:29:59 +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: [PATCH v3 4/6] sched/fair: Limit run to parity to the min slice of enqueued entities To: Vincent Guittot References: <20250708165630.1948751-1-vincent.guittot@linaro.org> <20250708165630.1948751-5-vincent.guittot@linaro.org> Content-Language: en-US Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, dhaval@gianis.ca, linux-kernel@vger.kernel.org, Madadi Vineeth Reddy From: Madadi Vineeth Reddy In-Reply-To: <20250708165630.1948751-5-vincent.guittot@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Vaj3PEp9 c=1 sm=1 tr=0 ts=686f64f7 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=LmcLtsNzV1WpfnEq:21 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=KKAkSRfTAAAA:8 a=1loupnIqrAf6m2OXCqwA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-GUID: zZiTaS5GVENVCgO-xJjZXdyk3sbIGTHc X-Proofpoint-ORIG-GUID: pHZtI4CCz5R1n7RiMGMvIcJo6aaybHqe X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzEwMDA1NyBTYWx0ZWRfX4fPGG41OJ0Xl dyrGCwxmzfBFFSFTzm4a1Dz5Yw/3LNxomUI9JGDz4x5IP9EXrFl+6YYruTzbc8JyVz3r2bSc9Qk blxcVJ8VjhNef9aoegS7YBGVvVN72a5p0MD7NXoFTWlxiG9HPppwfdOkWV+2PMI6znjlfVCTZn0 +D6ClAbq0qUIUCRAdLzMufLGWnsuA7WV2dHtsd8g8x8bi/czNEkX6F2VBf9V3Yga4FsQYFPqSBj uUy/EWiO3Wz9ZQ/VhmJQk3Zv4aDWexz4Z6enwOHpgif6nPu5rYGwnHYBrMtG9pYAIX6SU0K/Q0Y HV1lEgIaxEYULUfjERlRQhCR+4WxUANbUfZ5sm1VrX0mCPnN+5a6zYz8fgL/LzW6zerSiTG/de7 x2FRMs8v5NoNyOJZlDQXiGwWtH8SlU6pDjIHCzI7rPYo+tAPaV8lw9rJbpmaKV3OY1g2vXCL X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-07-09_05,2025-07-09_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 clxscore=1011 adultscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 bulkscore=0 mlxscore=0 spamscore=0 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507100057 Hi Vincent, On 08/07/25 22:26, Vincent Guittot wrote: > Run to parity ensures that current will get a chance to run its full > slice in one go but this can create large latency and/or lag for > entities with shorter slice that have exhausted their previous slice > and wait to run their next slice. > > Clamp the run to parity to the shortest slice of all enqueued entities. > > Signed-off-by: Vincent Guittot > --- > kernel/sched/fair.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 7e82b357763a..85238f2e026a 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -884,16 +884,20 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) > /* > * Set the vruntime up to which an entity can run before looking > * for another entity to pick. > - * In case of run to parity, we protect the entity up to its deadline. > + * In case of run to parity, we use the shortest slice of the enqueued > + * entities to set the protected period. > * When run to parity is disabled, we give a minimum quantum to the running > * entity to ensure progress. > */ If I set my task’s custom slice to a larger value but another task has a smaller slice, this change will cap my protected window to the smaller slice. Does that mean my custom slice is no longer honored? Thanks, Madadi Vineeth Reddy > static inline void set_protect_slice(struct sched_entity *se) > { > - u64 quantum = se->slice; > + u64 quantum; > > - if (!sched_feat(RUN_TO_PARITY)) > - quantum = min(quantum, normalized_sysctl_sched_base_slice); > + if (sched_feat(RUN_TO_PARITY)) > + quantum = cfs_rq_min_slice(cfs_rq_of(se)); > + else > + quantum = normalized_sysctl_sched_base_slice; > + quantum = min(quantum, se->slice); > > if (quantum != se->slice) > se->vprot = min_vruntime(se->deadline, se->vruntime + calc_delta_fair(quantum, se));