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Thu, 7 Aug 2025 06:22:02 GMT Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3797158445; Thu, 7 Aug 2025 06:22:02 +0000 (GMT) Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1A1BB58440; Thu, 7 Aug 2025 06:21:57 +0000 (GMT) Received: from [9.67.88.77] (unknown [9.67.88.77]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 7 Aug 2025 06:21:56 +0000 (GMT) Message-ID: <22e5bd44-1bba-4cc4-be21-04bbd9702da8@linux.ibm.com> Date: Thu, 7 Aug 2025 11:51:54 +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] sched/fair: Update stale comments referencing last/skip buddy To: Zhongqiu Han Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, Adam Li , linux-kernel@vger.kernel.org References: <20250805122316.1097085-1-quic_zhonhan@quicinc.com> Content-Language: en-US From: Madadi Vineeth Reddy In-Reply-To: <20250805122316.1097085-1-quic_zhonhan@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODA3MDA0NyBTYWx0ZWRfX01d3TWcoC8ok HpZ6n4yO1nwRPZe5G3x8yWDW23gG6Dq5JyP+o6Q9KZG/ebQtXY2P7yKhANcgsqk600O31WT9da3 BzUTB6WJpg24JstBuFIkcJS9l1vXD7YU3wVXehrmE9fGj9cK8+zgevxJKUsiB5ae4Bi+wZJlsGr t76/bn6X8Wqqwwt4a6YBajWB+64CP+xNBH0Bb+6PQ+uF0iT2b5yWWQRa6sJJzeOzJvcsxqFTBzx 5qq6K9qLASccwlQQsABGAsGe/jPSEstYluRW+hPfp9jPa9cWy09ifwBqnrzNqu4UzzGWxh2u0u7 hpam1zHJAI69yIK9LqOB9lHXFLDHueUwEz0m+m8OwZ2xiUF4PrYXUqP5epYZfcfJkjhsD3/Lkbe RAFCoSsRHAnuRBA90bPIFdKJBAdMHJpJMoSvkQIy4SMQqbdmQrahsPYOHySNauAJBol1OaRN X-Proofpoint-ORIG-GUID: 0RpAP8Jhp4VEUdXhf8xYx5GuvcNA5Bo4 X-Authority-Analysis: v=2.4 cv=LreSymdc c=1 sm=1 tr=0 ts=6894460b cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=COk6AnOGAAAA:8 a=QltLfnY_znEH1c5NIH8A:9 a=QEXdDO2ut3YA:10 a=TjNXssC_j7lpFel5tvFf:22 X-Proofpoint-GUID: qLxO6T_c4yGcgzhreef38K8fCbts9MCI X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-06_05,2025-08-06_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1011 lowpriorityscore=0 phishscore=0 spamscore=0 priorityscore=1501 impostorscore=0 adultscore=0 mlxlogscore=999 bulkscore=0 malwarescore=0 mlxscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508070047 Hi Zhongqiu, On 05/08/25 17:53, Zhongqiu Han wrote: > Since the integration of EEVDF, the last/skip buddy scheduling features > have been removed. This patch updates outdated comments that still > reference these legacy behaviors to avoid inconsistencies. > > Fixes: 5e963f2bd465 ("sched/fair: Commit to EEVDF") > Signed-off-by: Zhongqiu Han > --- > kernel/sched/fair.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index b173a059315c..b3618aa075ec 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5500,11 +5500,11 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) > static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags); > > /* > - * Pick the next process, keeping these things in mind, in this order: > - * 1) keep things fair between processes/task groups > - * 2) pick the "next" process, since someone really wants that to run > - * 3) pick the "last" process, for cache locality > - * 4) do not run the "skip" process, if something else is available > + * Pick the next sched_entity to run from cfs_rq. > + * > + * Prefer ->next buddy if sched_feat(PICK_BUDDY) is enabled and it's eligible, > + * to improve cache locality. > + * Otherwise, pick the entity via EEVDF for fairness and latency control. > */ > static struct sched_entity * > pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq) > @@ -8673,9 +8673,9 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int > * > * Note: this also catches the edge-case of curr being in a throttled > * group (e.g. via set_curr_task), since update_curr() (in the > - * enqueue of curr) will have resulted in resched being set. This > - * prevents us from potentially nominating it as a false LAST_BUDDY > - * below. > + * enqueue of curr) will have resulted in resched being set. This > + * prevents further preemption handling, including checks and potential > + * reschedule triggering. > */ > if (test_tsk_need_resched(rq->curr)) > return; Sent similar patch here https://lore.kernel.org/lkml/20250314090128.25141-1-vineethr@linux.ibm.com/ [PATCH] sched/fair: Remove stale references to LAST_BUDDY and SKIP_BUDDY Thanks, Madadi Vineeth Reddy