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/gpu/amdgpu/driver-misc.rst | 156 +++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 Documentation/gpu/amdgpu/driver-misc.rst (limited to 'Documentation/gpu/amdgpu/driver-misc.rst') diff --git a/Documentation/gpu/amdgpu/driver-misc.rst b/Documentation/gpu/amdgpu/driver-misc.rst new file mode 100644 index 000000000..e1a964c3a --- /dev/null +++ b/Documentation/gpu/amdgpu/driver-misc.rst @@ -0,0 +1,156 @@ +================================ + Misc AMDGPU driver information +================================ + +GPU Product Information +======================= + +Information about the GPU can be obtained on certain cards +via sysfs + +product_name +------------ + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c + :doc: product_name + +product_number +-------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c + :doc: product_number + +serial_number +------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c + :doc: serial_number + +fru_id +------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c + :doc: fru_id + +manufacturer +------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c + :doc: manufacturer + +unique_id +--------- + +.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c + :doc: unique_id + +board_info +---------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_device.c + :doc: board_info + +GPU Memory Usage Information +============================ + +Various memory accounting can be accessed via sysfs + +mem_info_vram_total +------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c + :doc: mem_info_vram_total + +mem_info_vram_used +------------------ + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c + :doc: mem_info_vram_used + +mem_info_vis_vram_total +----------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c + :doc: mem_info_vis_vram_total + +mem_info_vis_vram_used +---------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c + :doc: mem_info_vis_vram_used + +mem_info_gtt_total +------------------ + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c + :doc: mem_info_gtt_total + +mem_info_gtt_used +----------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c + :doc: mem_info_gtt_used + +PCIe Accounting Information +=========================== + +pcie_bw +------- + +.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c + :doc: pcie_bw + +pcie_replay_count +----------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_device.c + :doc: pcie_replay_count + +GPU SmartShift Information +========================== + +GPU SmartShift information via sysfs + +smartshift_apu_power +-------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c + :doc: smartshift_apu_power + +smartshift_dgpu_power +--------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c + :doc: smartshift_dgpu_power + +smartshift_bias +--------------- + +.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c + :doc: smartshift_bias + +UMA Carveout +============ + +Some versions of Atom ROM expose available options for the VRAM carveout sizes, +and allow changes to the carveout size via the ATCS function code 0xA on supported +BIOS implementations. + +For those platforms, users can use the following files under uma/ to set the +carveout size, in a way similar to what Windows users can do in the "Tuning" +tab in AMD Adrenalin. + +Note that for BIOS implementations that don't support this, these files will not +be created at all. + +uma/carveout_options +-------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_device.c + :doc: uma/carveout_options + +uma/carveout +-------------------- + +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_device.c + :doc: uma/carveout -- cgit v1.3.1