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/panfrost.rst | 49 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 Documentation/gpu/panfrost.rst (limited to 'Documentation/gpu/panfrost.rst') diff --git a/Documentation/gpu/panfrost.rst b/Documentation/gpu/panfrost.rst new file mode 100644 index 000000000..51ba375fd --- /dev/null +++ b/Documentation/gpu/panfrost.rst @@ -0,0 +1,49 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +========================= + drm/Panfrost Mali Driver +========================= + +.. _panfrost-usage-stats: + +Panfrost DRM client usage stats implementation +============================================== + +The drm/Panfrost driver implements the DRM client usage stats specification as +documented in :ref:`drm-client-usage-stats`. + +Example of the output showing the implemented key value pairs and entirety of +the currently possible format options: + +:: + pos: 0 + flags: 02400002 + mnt_id: 27 + ino: 531 + drm-driver: panfrost + drm-client-id: 14 + drm-engine-fragment: 1846584880 ns + drm-cycles-fragment: 1424359409 + drm-maxfreq-fragment: 799999987 Hz + drm-curfreq-fragment: 799999987 Hz + drm-engine-vertex-tiler: 71932239 ns + drm-cycles-vertex-tiler: 52617357 + drm-maxfreq-vertex-tiler: 799999987 Hz + drm-curfreq-vertex-tiler: 799999987 Hz + drm-total-memory: 290 MiB + drm-shared-memory: 0 MiB + drm-active-memory: 226 MiB + drm-resident-memory: 36496 KiB + drm-purgeable-memory: 128 KiB + +Possible `drm-engine-` key names are: `fragment`, and `vertex-tiler`. +`drm-curfreq-` values convey the current operating frequency for that engine. + +Users must bear in mind that engine and cycle sampling are disabled by default, +because of power saving concerns. `fdinfo` users and benchmark applications which +query the fdinfo file must make sure to toggle the job profiling status of the +driver by writing into the appropriate sysfs node:: + + echo > /sys/bus/platform/drivers/panfrost/[a-f0-9]*.gpu/profiling + +Where `N` is either `0` or `1`, depending on the desired enablement status. -- cgit v1.3.1