From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- Documentation/ABI/testing/amdpmf-interface | 73 ++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 Documentation/ABI/testing/amdpmf-interface (limited to 'Documentation/ABI/testing/amdpmf-interface') diff --git a/Documentation/ABI/testing/amdpmf-interface b/Documentation/ABI/testing/amdpmf-interface new file mode 100644 index 000000000..625f90a01 --- /dev/null +++ b/Documentation/ABI/testing/amdpmf-interface @@ -0,0 +1,73 @@ +What: /dev/amdpmf_interface +Date: June 2026 +KernelVersion: 7.2 +Contact: Shyam Sundar S K +Description: + The AMD Platform Management Framework (PMF) util layer exposes a + minimal user-space interface via a character device for feature + discovery and metrics monitoring. + + When CONFIG_AMD_PMF_UTIL_SUPPORT is enabled, the driver creates + a character device: + + ====================== + /dev/amdpmf_interface + ====================== + + The interface supports a single ioctl: + + ============================ ======================================= + IOCTL Usage + IOCTL_AMD_PMF_POPULATE_DATA User passes a struct amd_pmf_info with + the size field set to sizeof(struct + amd_pmf_info). The driver returns all + available metrics and feature status + in the structure. + ============================ ======================================= + + struct amd_pmf_info layout: + + ======================= ========== ================================ + Field Type Description + size __u64 Structure size for versioning + features_supported __u32 Bitmask of supported features + platform_type __u32 Platform form factor orientation + power_source __u32 AC/DC power source + laptop_placement __u32 Device placement state + lid_state __u32 Lid open/closed status + user_presence __u32 User presence detection + slider_position __u32 Current power slider position + skin_temp __s32 Skin temperature (centidegrees) + gfx_busy __u32 Graphics workload percentage + ambient_light __s32 Ambient light sensor reading + avg_c0_residency __u32 Average C0 state residency + max_c0_residency __u32 Maximum C0 state residency + socket_power __u32 Socket power consumption + bios_input[10] __u32 Custom BIOS input parameters + bios_output[10] __u32 Custom BIOS output parameters + ======================= ========== ================================ + + Feature Support Flags (features_supported bitmask): + + ===================================== ==== ============================= + Flag Bit Description + AMD_PMF_FEAT_AUTO_MODE 0 Auto Mode feature support + AMD_PMF_FEAT_STATIC_POWER_SLIDER 1 Static Power Slider support + AMD_PMF_FEAT_POLICY_BUILDER 2 Policy Builder (Smart PC) + AMD_PMF_FEAT_DYNAMIC_POWER_SLIDER_AC 3 Dynamic slider on AC + AMD_PMF_FEAT_DYNAMIC_POWER_SLIDER_DC 4 Dynamic slider on DC + ===================================== ==== ============================= + + Return codes: + + ============= ============================================================ + Return code Description + 0 Success + EINVAL Invalid size or parameter + EFAULT copy_to_user/copy_from_user failures + ENODEV PMF device not available + ENOTTY Unknown ioctl command + ============= ============================================================ + + User-space tools integrating with AMD PMF to discover capabilities and + monitor real-time metrics for thermal and power management validation. -- cgit v1.3.1