linux-toradex.git/kernel/sched/stats.c, branch v6.19

sched/smp: Use the SMP version of schedstats

2025-06-13T06:47:21+00:00

Simplify the scheduler by making CONFIG_SMP=y schedstats
debugging output unconditional.

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-32-mingo@kernel.org

sched: Clean up and standardize #if/#else/#endif markers in sched/stats.[ch]

2025-06-13T06:47:17+00:00

 - Use the standard #ifdef marker format for larger blocks,
   where appropriate:

        #if CONFIG_FOO
        ...
        #else /* !CONFIG_FOO: */
        ...
        #endif /* !CONFIG_FOO */

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-17-mingo@kernel.org

sched: Make clangd usable

2025-06-11T09:20:53+00:00

Due to the weird Makefile setup of sched the various files do not
compile as stand alone units. The new generation of editors are trying
to do just this -- mostly to offer fancy things like completions but
also better syntax highlighting and code navigation.

Specifically, I've been playing around with neovim and clangd.

Setting up clangd on the kernel source is a giant pain in the arse
(this really should be improved), but once you do manage, you run into
dumb stuff like the above.

Fix up the scheduler files to at least pretend to work.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Ingo Molnar 
Tested-by: Juri Lelli 
Link: https://lkml.kernel.org/r/20250523164348.GN39944@noisy.programming.kicks-ass.net

docs: Update Schedstat version to 17

2024-12-20T14:31:18+00:00

Update the Schedstat version to 17 as more fields are added to report
different kinds of imbalances in the sched domain. Also domain field
started printing corresponding domain name.

Signed-off-by: Swapnil Sapkal 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20241220063224.17767-7-swapnil.sapkal@amd.com

sched/stats: Print domain name in /proc/schedstat

2024-12-20T14:31:18+00:00

Currently, there does not exist a straightforward way to extract the
names of the sched domains and match them to the per-cpu domain entry in
/proc/schedstat other than looking at the debugfs files which are only
visible after enabling "verbose" debug after commit 34320745dfc9
("sched/debug: Put sched/domains files under the verbose flag")

Since tools like `perf sched stats`[1] require displaying per-domain
information in user friendly manner, display the names of sched domain,
alongside their level in /proc/schedstat.

Domain names also makes the /proc/schedstat data unambiguous when some
of the cpus are offline. For example, on a 128 cpus AMD Zen3 machine
where CPU0 and CPU64 are SMT siblings and CPU64 is offline:

Before:
    cpu0 ...
    domain0 ...
    domain1 ...
    cpu1 ...
    domain0 ...
    domain1 ...
    domain2 ...

After:
    cpu0 ...
    domain0 MC ...
    domain1 PKG ...
    cpu1 ...
    domain0 SMT ...
    domain1 MC ...
    domain2 PKG ...

[1] https://lore.kernel.org/lkml/20241122084452.1064968-1-swapnil.sapkal@amd.com/

Signed-off-by: K Prateek Nayak 
Signed-off-by: Ravi Bangoria 
Signed-off-by: Swapnil Sapkal 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: James Clark 
Link: https://lore.kernel.org/r/20241220063224.17767-6-swapnil.sapkal@amd.com

sched: Report the different kinds of imbalances in /proc/schedstat

2024-12-20T14:31:17+00:00

In /proc/schedstat, lb_imbalance reports the sum of imbalances
discovered in sched domains with each call to sched_balance_rq(), which is
not very useful because lb_imbalance does not mention whether the imbalance
is due to load, utilization, nr_tasks or misfit_tasks. Remove this field
from /proc/schedstat.

Currently there is no field in /proc/schedstat to report different types
of imbalances. Introduce new fields in /proc/schedstat to report the
total imbalances in load, utilization, nr_tasks or misfit_tasks.

Added fields to /proc/schedstat:
        - lb_imbalance_load: Total imbalance due to load.
        - lb_imbalance_util: Total imbalance due to utilization.
        - lb_imbalance_task: Total imbalance due to number of tasks.
        - lb_imbalance_misfit: Total imbalance due to misfit tasks.

Signed-off-by: Swapnil Sapkal 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Shrikanth Hegde 
Link: https://lore.kernel.org/r/20241220063224.17767-4-swapnil.sapkal@amd.com

profiling: remove profile=sleep support

2024-08-04T20:36:28+00:00

The kernel sleep profile is no longer working due to a recursive locking
bug introduced by commit 42a20f86dc19 ("sched: Add wrapper for get_wchan()
to keep task blocked")

Booting with the 'profile=sleep' kernel command line option added or
executing

  # echo -n sleep > /sys/kernel/profiling

after boot causes the system to lock up.

Lockdep reports

  kthreadd/3 is trying to acquire lock:
  ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: get_wchan+0x32/0x70

  but task is already holding lock:
  ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: try_to_wake_up+0x53/0x370

with the call trace being

   lock_acquire+0xc8/0x2f0
   get_wchan+0x32/0x70
   __update_stats_enqueue_sleeper+0x151/0x430
   enqueue_entity+0x4b0/0x520
   enqueue_task_fair+0x92/0x6b0
   ttwu_do_activate+0x73/0x140
   try_to_wake_up+0x213/0x370
   swake_up_locked+0x20/0x50
   complete+0x2f/0x40
   kthread+0xfb/0x180

However, since nobody noticed this regression for more than two years,
let's remove 'profile=sleep' support based on the assumption that nobody
needs this functionality.

Fixes: 42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep task blocked")
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Tetsuo Handa 
Signed-off-by: Linus Torvalds

sched/debug: Increase SCHEDSTAT_VERSION to 16

2024-03-12T10:03:40+00:00

We changed the order of definitions within 'enum cpu_idle_type',
which changed the order of [CPU_MAX_IDLE_TYPES] columns in
show_schedstat().

Suggested-by: Shrikanth Hegde 
Signed-off-by: Ingo Molnar 
Cc: "Gautham R. Shenoy" 
Link: https://lore.kernel.org/r/20240308105901.1096078-5-mingo@kernel.org

sched/balancing: Remove reliance on 'enum cpu_idle_type' ordering when iterating [CPU_MAX_IDLE_TYPES] arrays in show_schedstat()

2024-03-12T10:03:40+00:00

show_schedstat() output breaks and doesn't print all entries
if the ordering of the definitions in 'enum cpu_idle_type' is changed,
because show_schedstat() assumes that 'CPU_IDLE' is 0.

Fix it before we change the definition order & values.

[ mingo: Added changelog. ]

Signed-off-by: Shrikanth Hegde 
Signed-off-by: Ingo Molnar 
Reviewed-by: Vincent Guittot 
Link: https://lore.kernel.org/r/20240308105901.1096078-3-mingo@kernel.org

sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there

2022-02-23T09:58:33+00:00

Collect all utility functionality source code files into a single kernel/sched/build_utility.c file,
via #include-ing the .c files:

    kernel/sched/clock.c
    kernel/sched/completion.c
    kernel/sched/loadavg.c
    kernel/sched/swait.c
    kernel/sched/wait_bit.c
    kernel/sched/wait.c

CONFIG_CPU_FREQ:
    kernel/sched/cpufreq.c

CONFIG_CPU_FREQ_GOV_SCHEDUTIL:
    kernel/sched/cpufreq_schedutil.c

CONFIG_CGROUP_CPUACCT:
    kernel/sched/cpuacct.c

CONFIG_SCHED_DEBUG:
    kernel/sched/debug.c

CONFIG_SCHEDSTATS:
    kernel/sched/stats.c

CONFIG_SMP:
   kernel/sched/cpupri.c
   kernel/sched/stop_task.c
   kernel/sched/topology.c

CONFIG_SCHED_CORE:
   kernel/sched/core_sched.c

CONFIG_PSI:
   kernel/sched/psi.c

CONFIG_MEMBARRIER:
   kernel/sched/membarrier.c

CONFIG_CPU_ISOLATION:
   kernel/sched/isolation.c

CONFIG_SCHED_AUTOGROUP:
   kernel/sched/autogroup.c

The goal is to amortize the 60+ KLOC header bloat from over a dozen build units into
a single build unit.

The build time of build_utility.c also roughly matches the build time of core.c and
fair.c - allowing better load-balancing of scheduler-only rebuilds.

Signed-off-by: Ingo Molnar 
Reviewed-by: Peter Zijlstra