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Shenoy" , Vincent Guittot , Chen Yu , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Hillf Danton , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , Vern Hao , Len Brown , Aubrey Li , Zhao Liu , Chen Yu , Adam Li , Aaron Lu , Tim Chen , Josh Don , Gavin Guo , Qais Yousef , Libo Chen , linux-kernel@vger.kernel.org, Madadi Vineeth Reddy References: <20260219165221.GM1395266@noisy.programming.kicks-ass.net> Content-Language: en-US From: Madadi Vineeth Reddy In-Reply-To: <20260219165221.GM1395266@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjIwMDA1NyBTYWx0ZWRfX1mqv6wp9hL9s F/exq142m0msEWxrlxDMIDYMalMxRYPSDnrSPbdT08uIRGzrWevo8fSifsqpBHIu4w0RZW4QPvh 8Po9DJwhJLlMdZ68LpEI2FcJiq5cmfrYUolP1DVLW5jGAh29cedSRIWdniUHURAdiVG/zwycgZS uq29JTDyZJXO9eN0kzjrezpuv2oRRPEG38RULkgXnDev1f5pRBsF3Mv7R/dGDxdv4I4ajA8PzdN mwCbPK+p+AkEvekSfKy8LAq2sH4xjAbgB3dzNYZ+U9rL4fmL4fcSo3HGYXOy1byJVfBjS6kSbtR wcEGOO3ZAZxHqmmyXFvYHmk6nSHFR5cE4v6qtMKXxekFhbE7flMyX7LYd2k7y2eS5FiHkut+PGz lvqCN1yzSU21vlV+jjXg3AO+A2FEGIBHejtuM3hsfzklySg1pBpT0M9TWKAAeAdjw1tIueVMwMh c/f99999s3kqYKAhHdA== X-Proofpoint-ORIG-GUID: n5RHVv-r-beKbnxFHmy9KbKGedx1HhQR X-Proofpoint-GUID: S_su-0jMh_PxRwlvEK-bNOIclKzQ_Hwa X-Authority-Analysis: v=2.4 cv=M7hA6iws c=1 sm=1 tr=0 ts=69980714 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=6JLQv9UL4AW_bNQ1u0sA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-19_06,2026-02-20_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 malwarescore=0 lowpriorityscore=0 clxscore=1015 phishscore=0 impostorscore=0 suspectscore=0 priorityscore=1501 adultscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602200057 On 19/02/26 22:22, Peter Zijlstra wrote: > On Wed, Feb 18, 2026 at 11:24:05PM +0530, Madadi Vineeth Reddy wrote: > >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index d1145997b88d..86b6b08e7e1e 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -1223,6 +1223,19 @@ static inline bool valid_llc_buf(struct sched_domain *sd, >>> return valid_llc_id(id); >>> } >>> >>> +static bool exceed_llc_nr(struct mm_struct *mm, int cpu) >>> +{ >>> + int smt_nr = 1; >>> + >>> +#ifdef CONFIG_SCHED_SMT >>> + if (sched_smt_active()) >>> + smt_nr = cpumask_weight(cpu_smt_mask(cpu)); >>> +#endif >>> + >>> + return !fits_capacity((mm->sc_stat.nr_running_avg * smt_nr), >>> + per_cpu(sd_llc_size, cpu)); >> >> >> On Power10/Power11 with SMT4 and LLC size of 4, this check >> effectively disables cache-aware scheduling for any process. >> >> I raised this point in v1 as well. Increasing the threshold >> doesn't seem like a viable solution either, as that would regress >> hackbench/ebizzy. >> >> Is there a way to make this useful for architectures with small LLC >> sizes? One possible approach we were exploring is to have LLC at a >> hemisphere level that comprise multiple SMT4 cores. > > One way forward would be to use a llc-mask instead of a single llc value > for preference. I think this got mentioned before, and I think it makes > sense to do this later. > > But once you can have a 'few' LLCs as preference, this constraint > becomes a little easier. Yes, that makes sense. Spanning the llc-mask across multiple cores in a hemisphere for preference would relax this condition. We will explore how this can be incorporated. Thanks for taking a look. Thanks, Vineeth