linux/kernel/time
Linus Torvalds ed3b7923a8 Scheduler changes for v6.5:
- Scheduler SMP load-balancer improvements:
 
     - Avoid unnecessary migrations within SMT domains on hybrid systems.
 
       Problem:
 
         On hybrid CPU systems, (processors with a mixture of higher-frequency
 	SMT cores and lower-frequency non-SMT cores), under the old code
 	lower-priority CPUs pulled tasks from the higher-priority cores if
 	more than one SMT sibling was busy - resulting in many unnecessary
 	task migrations.
 
       Solution:
 
         The new code improves the load balancer to recognize SMT cores with more
         than one busy sibling and allows lower-priority CPUs to pull tasks, which
         avoids superfluous migrations and lets lower-priority cores inspect all SMT
         siblings for the busiest queue.
 
     - Implement the 'runnable boosting' feature in the EAS balancer: consider CPU
       contention in frequency, EAS max util & load-balance busiest CPU selection.
 
       This improves CPU utilization for certain workloads, while leaves other key
       workloads unchanged.
 
 - Scheduler infrastructure improvements:
 
     - Rewrite the scheduler topology setup code by consolidating it
       into the build_sched_topology() helper function and building
       it dynamically on the fly.
 
     - Resolve the local_clock() vs. noinstr complications by rewriting
       the code: provide separate sched_clock_noinstr() and
       local_clock_noinstr() functions to be used in instrumentation code,
       and make sure it is all instrumentation-safe.
 
 - Fixes:
 
     - Fix a kthread_park() race with wait_woken()
 
     - Fix misc wait_task_inactive() bugs unearthed by the -rt merge:
        - Fix UP PREEMPT bug by unifying the SMP and UP implementations.
        - Fix task_struct::saved_state handling.
 
     - Fix various rq clock update bugs, unearthed by turning on the rq clock
       debugging code.
 
     - Fix the PSI WINDOW_MIN_US trigger limit, which was easy to trigger by
       creating enough cgroups, by removing the warnign and restricting
       window size triggers to PSI file write-permission or CAP_SYS_RESOURCE.
 
     - Propagate SMT flags in the topology when removing degenerate domain
 
     - Fix grub_reclaim() calculation bug in the deadline scheduler code
 
     - Avoid resetting the min update period when it is unnecessary, in
       psi_trigger_destroy().
 
     - Don't balance a task to its current running CPU in load_balance(),
       which was possible on certain NUMA topologies with overlapping
       groups.
 
     - Fix the sched-debug printing of rq->nr_uninterruptible
 
 - Cleanups:
 
     - Address various -Wmissing-prototype warnings, as a preparation
       to (maybe) enable this warning in the future.
 
     - Remove unused code
 
     - Mark more functions __init
 
     - Fix shadow-variable warnings
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "Scheduler SMP load-balancer improvements:

   - Avoid unnecessary migrations within SMT domains on hybrid systems.

     Problem:

        On hybrid CPU systems, (processors with a mixture of
        higher-frequency SMT cores and lower-frequency non-SMT cores),
        under the old code lower-priority CPUs pulled tasks from the
        higher-priority cores if more than one SMT sibling was busy -
        resulting in many unnecessary task migrations.

     Solution:

        The new code improves the load balancer to recognize SMT cores
        with more than one busy sibling and allows lower-priority CPUs
        to pull tasks, which avoids superfluous migrations and lets
        lower-priority cores inspect all SMT siblings for the busiest
        queue.

   - Implement the 'runnable boosting' feature in the EAS balancer:
     consider CPU contention in frequency, EAS max util & load-balance
     busiest CPU selection.

     This improves CPU utilization for certain workloads, while leaves
     other key workloads unchanged.

  Scheduler infrastructure improvements:

   - Rewrite the scheduler topology setup code by consolidating it into
     the build_sched_topology() helper function and building it
     dynamically on the fly.

   - Resolve the local_clock() vs. noinstr complications by rewriting
     the code: provide separate sched_clock_noinstr() and
     local_clock_noinstr() functions to be used in instrumentation code,
     and make sure it is all instrumentation-safe.

  Fixes:

   - Fix a kthread_park() race with wait_woken()

   - Fix misc wait_task_inactive() bugs unearthed by the -rt merge:
       - Fix UP PREEMPT bug by unifying the SMP and UP implementations
       - Fix task_struct::saved_state handling

   - Fix various rq clock update bugs, unearthed by turning on the rq
     clock debugging code.

   - Fix the PSI WINDOW_MIN_US trigger limit, which was easy to trigger
     by creating enough cgroups, by removing the warnign and restricting
     window size triggers to PSI file write-permission or
     CAP_SYS_RESOURCE.

   - Propagate SMT flags in the topology when removing degenerate domain

   - Fix grub_reclaim() calculation bug in the deadline scheduler code

   - Avoid resetting the min update period when it is unnecessary, in
     psi_trigger_destroy().

   - Don't balance a task to its current running CPU in load_balance(),
     which was possible on certain NUMA topologies with overlapping
     groups.

   - Fix the sched-debug printing of rq->nr_uninterruptible

  Cleanups:

   - Address various -Wmissing-prototype warnings, as a preparation to
     (maybe) enable this warning in the future.

   - Remove unused code

   - Mark more functions __init

   - Fix shadow-variable warnings"

* tag 'sched-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
  sched/core: Avoid multiple calling update_rq_clock() in __cfsb_csd_unthrottle()
  sched/core: Avoid double calling update_rq_clock() in __balance_push_cpu_stop()
  sched/core: Fixed missing rq clock update before calling set_rq_offline()
  sched/deadline: Update GRUB description in the documentation
  sched/deadline: Fix bandwidth reclaim equation in GRUB
  sched/wait: Fix a kthread_park race with wait_woken()
  sched/topology: Mark set_sched_topology() __init
  sched/fair: Rename variable cpu_util eff_util
  arm64/arch_timer: Fix MMIO byteswap
  sched/fair, cpufreq: Introduce 'runnable boosting'
  sched/fair: Refactor CPU utilization functions
  cpuidle: Use local_clock_noinstr()
  sched/clock: Provide local_clock_noinstr()
  x86/tsc: Provide sched_clock_noinstr()
  clocksource: hyper-v: Provide noinstr sched_clock()
  clocksource: hyper-v: Adjust hv_read_tsc_page_tsc() to avoid special casing U64_MAX
  x86/vdso: Fix gettimeofday masking
  math64: Always inline u128 version of mul_u64_u64_shr()
  s390/time: Provide sched_clock_noinstr()
  loongarch: Provide noinstr sched_clock_read()
  ...
2023-06-27 14:03:21 -07:00
..
alarmtimer.c alarmtimer: Remove unnecessary (void *) cast 2023-06-18 22:41:53 +02:00
clockevents.c clockevents: Repair kernel-doc for clockevent_delta2ns() 2022-12-01 13:35:41 +01:00
clocksource-wdtest.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
clocksource.c clocksource: Suspend the watchdog temporarily when high read latency detected 2023-01-24 15:12:48 -08:00
hrtimer.c hrtimer: Add missing sparse annotations to hrtimer locking 2023-06-22 10:32:37 +02:00
itimer.c time: Prevent undefined behaviour in timespec64_to_ns() 2020-10-26 11:48:11 +01:00
jiffies.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
Kconfig clocksource: Loosen clocksource watchdog constraints 2023-01-03 20:43:45 -08:00
Makefile time: Improve performance of time64_to_tm() 2021-06-24 11:51:59 +02:00
namespace.c vdso/timens: Refactor copy-pasted find_timens_vvar_page() helper into one copy 2022-12-01 11:35:40 +01:00
ntp_internal.h ntp: Make the RTC synchronization more reliable 2020-12-11 10:40:52 +01:00
ntp.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
posix-clock.c posix-clocks: Rename the clock_get() callback to clock_get_timespec() 2020-01-14 12:20:49 +01:00
posix-cpu-timers.c posix-cpu-timers: Implement the missing timer_wait_running callback 2023-04-21 15:34:33 +02:00
posix-stubs.c timers: Prevent union confusion from unexpected restart_syscall() 2023-01-11 19:31:47 +01:00
posix-timers.c posix-timers: Refer properly to CONFIG_HIGH_RES_TIMERS 2023-06-18 22:41:53 +02:00
posix-timers.h posix-clocks: Introduce clock_get_ktime() callback 2020-01-14 12:20:51 +01:00
sched_clock.c time/sched_clock: Provide sched_clock_noinstr() 2023-06-05 21:11:04 +02:00
test_udelay.c time/debug: Fix memory leak with using debugfs_lookup() 2023-02-09 20:12:27 +01:00
tick-broadcast-hrtimer.c time/tick-broadcast: Remove RCU_NONIDLE() usage 2023-01-13 11:48:16 +01:00
tick-broadcast.c tick/broadcast: Make broadcast device replacement work correctly 2023-05-08 23:18:16 +02:00
tick-common.c tick/common: Align tick period during sched_timer setup 2023-06-16 20:45:28 +02:00
tick-internal.h clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
tick-legacy.c timekeeping: remove xtime_update 2020-10-30 21:57:07 +01:00
tick-oneshot.c time: Fix various kernel-doc problems 2023-01-03 11:07:58 +01:00
tick-sched.c Time, timekeeping and related device driver updates: 2023-06-26 14:10:45 -07:00
tick-sched.h timers/nohz: Protect idle/iowait sleep time under seqcount 2023-04-18 16:35:12 +02:00
time_test.c time/kunit: Add missing MODULE_LICENSE() 2021-06-28 07:40:23 +02:00
time.c time: Fix various kernel-doc problems 2023-01-03 11:07:58 +01:00
timeconst.bc time: Add SPDX license identifiers 2018-11-23 11:51:20 +01:00
timeconv.c time: Improve performance of time64_to_tm() 2021-06-24 11:51:59 +02:00
timecounter.c time/timecounter: Mark 1st argument of timecounter_cyc2time() as const 2021-04-16 21:03:50 +02:00
timekeeping_debug.c timekeeping/debug: No need to check return value of debugfs_create functions 2019-01-29 20:08:41 +01:00
timekeeping_internal.h timekeeping/vsyscall: Provide vdso_update_begin/end() 2020-08-06 10:57:30 +02:00
timekeeping.c seqlock/latch: Provide raw_read_seqcount_latch_retry() 2023-06-05 21:11:03 +02:00
timekeeping.h asm-generic: cross-architecture timer cleanup 2020-12-16 00:07:17 -08:00
timer_list.c timer_list: Print name of per-cpu wakeup device 2021-05-31 17:04:49 +02:00
timer.c timers: Provide timer_shutdown[_sync]() 2022-11-24 15:09:12 +01:00
vsyscall.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00