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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: xUGt/dGe2PmB1eL30Jwzm7xhCC+d2JXfzGQLet00rujdTsf3oYgLxPhTS6dSspDt3AdYZv21Kt+OwOlnoNm1rxhY6+bHaRXBqvqa8+GDW2O4pzUR5/olIq6a7ypfg/nNCMX85vKAR/F0NqIXJbXEIx5wpzfZM6U2PMVgFGvQROqhYfuNVJTHizRkhKAL+Xsxxb5tq80668/PCz4N0j23GZojI5131lqv7LzH1lQRiZ6ioYMupgbhM2cLDxyiklA1h+Lv18XmUcESeJ2oA1eIkbMhjfiB0sTSUA848bQfdsLU2V8LAYtUa3yfPytXQMLdmWLZELn66t3YrN5MZ7RnH8kStbVVtFL+g3zTTy1iWBdOv0Cy2UmRpqdXnNh4LNCDgwRQi/yZNd7U4oa86EKBHfP8kNl4VXW1aTMBsByysdRsNX7p4atYWM9BtJ0vw9UM X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Feb 2026 05:20:58.4872 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 276bbbb2-1d71-4277-52b6-08de653f82d1 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00006001.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9234 Hello Valentin, On 2/5/2026 10:23 PM, Valentin Schneider wrote: > On 20/01/26 11:32, K Prateek Nayak wrote: >> @@ -2655,8 +2655,19 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att >> unsigned int imb_span = 1; >> >> for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { >> + struct sched_domain *parent = sd->parent; >> struct sched_domain *child = sd->child; >> >> + /* Attach sd->shared to the topmost SD_SHARE_LLC domain. */ >> + if ((sd->flags & SD_SHARE_LLC) && >> + (!parent || !(parent->flags & SD_SHARE_LLC))) { >> + int llc_id = cpumask_first(sched_domain_span(sd)); >> + >> + sd->shared = *per_cpu_ptr(d.sds, llc_id); >> + atomic_set(&sd->shared->nr_busy_cpus, sd->span_weight); >> + atomic_inc(&sd->shared->ref); >> + } >> + > > We now have two if's looking for the highest_flag_domain(i, SD_SHARE_LLC), > but given this needs to write the sd->imb_numa_nr for every SD I couldn't > factorize this into something that looked sane :( Yeah! The "imb_numa_nr" cares about the "sd_llc" *after* we've crossed it and "sd->shared" assignment cares when we are *at* the sd_llc. Since we have to assign the "sd->shared" before claim_allocations(), I couldn't find a better spot to assign it. That said, "imb_numa_nr" calculation can be modified to use the "sd_llc" and its "parent". I'll let you be the judge of whether the following is better or worse ;-) (Only build tested) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index ac268da91778..e98bb812de35 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2614,13 +2614,23 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att unsigned int imb_span = 1; for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { - struct sched_domain *child = sd->child; + struct sched_domain *parent = sd->parent; - if (!(sd->flags & SD_SHARE_LLC) && child && - (child->flags & SD_SHARE_LLC)) { - struct sched_domain __rcu *top_p; + /* Topmost SD_SHARE_LLC domain. */ + if ((sd->flags & SD_SHARE_LLC) && + (!parent || !(parent->flags & SD_SHARE_LLC))) { + int sd_id = cpumask_first(sched_domain_span(sd)); + struct sched_domain *top_p; unsigned int nr_llcs; + sd->shared = *per_cpu_ptr(d.sds, sd_id); + atomic_set(&sd->shared->nr_busy_cpus, sd->span_weight); + atomic_inc(&sd->shared->ref); + + /* No SD_NUMA domains. */ + if (!parent) + break; + /* * For a single LLC per node, allow an * imbalance up to 12.5% of the node. This is @@ -2641,7 +2651,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att * factors and that there is a correlation * between LLCs and memory channels. */ - nr_llcs = sd->span_weight / child->span_weight; + nr_llcs = parent->span_weight / sd->span_weight; if (nr_llcs == 1) imb = sd->span_weight >> 3; else @@ -2650,11 +2660,11 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att sd->imb_numa_nr = imb; /* Set span based on the first NUMA domain. */ - top_p = sd->parent; + top_p = parent; while (top_p && !(top_p->flags & SD_NUMA)) { top_p = top_p->parent; } - imb_span = top_p ? top_p->span_weight : sd->span_weight; + imb_span = top_p ? top_p->span_weight : parent->span_weight; } else { int factor = max(1U, (sd->span_weight / imb_span)); --- > >> if (!(sd->flags & SD_SHARE_LLC) && child && >> (child->flags & SD_SHARE_LLC)) { >> struct sched_domain __rcu *top_p; > -- Thanks and Regards, Prateek