[GIT PULL] scheduler updates for v5.12

From: Ingo Molnar
Date: Wed Feb 17 2021 - 08:44:21 EST


Please pull the latest sched/core git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-core-2021-02-17

# HEAD: c5e6fc08feb2b88dc5dac2f3c817e1c2a4cafda4 sched,x86: Allow !PREEMPT_DYNAMIC

Scheduler updates for v5.12:

[ NOTE: unfortunately this tree had to be freshly rebased today,
it's a same-content tree of 82891be90f3c (-next published)
merged with v5.11.

The main reason for the rebase was an authorship misattribution
problem with a new commit, which we noticed in the last minute,
and which we didn't want to be merged upstream. The offending
commit was deep in the tree, and dependent commits had to be
rebased as well. ]

- Core scheduler updates:

- Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the
preempt=none/voluntary/full boot options (default: full),
to allow distros to build a PREEMPT kernel but fall back to
close to PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling
behavior via a boot time selection.

There's also the /debug/sched_debug switch to do this runtime.

This feature is implemented via runtime patching (a new variant of static calls).

The scope of the runtime patching can be best reviewed by looking
at the sched_dynamic_update() function in kernel/sched/core.c.

( Note that the dynamic none/voluntary mode isn't 100% identical,
for example preempt-RCU is available in all cases, plus the
preempt count is maintained in all models, which has runtime
overhead even with the code patching. )

The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast majority
of distributions, are supposed to be unaffected.

- Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that
was found via rcutorture triggering a hang. The bug is that
rcu_idle_enter() may wake up a NOCB kthread, but this happens after
the last generic need_resched() check. Some cpuidle drivers fix it
by chance but many others don't.

In true 2020 fashion the original bug fix has grown into a 5-patch
scheduler/RCU fix series plus another 16 RCU patches to address
the underlying issue of missed preemption events. These are the
initial fixes that should fix current incarnations of the bug.

- Clean up rbtree usage in the scheduler, by providing & using the following
consistent set of rbtree APIs:

partial-order; less() based:
- rb_add(): add a new entry to the rbtree
- rb_add_cached(): like rb_add(), but for a rb_root_cached

total-order; cmp() based:
- rb_find(): find an entry in an rbtree
- rb_find_add(): find an entry, and add if not found

- rb_find_first(): find the first (leftmost) matching entry
- rb_next_match(): continue from rb_find_first()
- rb_for_each(): iterate a sub-tree using the previous two

- Improve the SMP/NUMA load-balancer: scan for an idle sibling in a single pass.
This is a 4-commit series where each commit improves one aspect of the idle
sibling scan logic.

- Improve the cpufreq cooling driver by getting the effective CPU utilization
metrics from the scheduler

- Improve the fair scheduler's active load-balancing logic by reducing the number
of active LB attempts & lengthen the load-balancing interval. This improves
stress-ng mmapfork performance.

- Fix CFS's estimated utilization (util_est) calculation bug that can result in
too high utilization values

- Misc updates & fixes:

- Fix the HRTICK reprogramming & optimization feature
- Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code
- Reduce dl_add_task_root_domain() overhead
- Fix uprobes refcount bug
- Process pending softirqs in flush_smp_call_function_from_idle()
- Clean up task priority related defines, remove *USER_*PRIO and
- Simplify the sched_init_numa() deduplication sort
- Documentation updates
- Fix EAS bug in update_misfit_status(), which degraded the quality
of energy-balancing
- Smaller cleanups



Anna-Maria Behnsen (1):
sched: Prevent raising SCHED_SOFTIRQ when CPU is !active

Dietmar Eggemann (5):
sched/topology: Fix sched_domain_topology_level alloc in sched_init_numa()
sched: Remove MAX_USER_RT_PRIO
sched/core: Update task_prio() function header
sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()

Frederic Weisbecker (6):
static_call: Provide DEFINE_STATIC_CALL_RET0()
rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers
rcu/nocb: Perform deferred wake up before last idle's need_resched() check
rcu/nocb: Trigger self-IPI on late deferred wake up before user resume
entry: Explicitly flush pending rcuog wakeup before last rescheduling point
entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point

Hui Su (1):
sched: Use task_current() instead of 'rq->curr == p'

Josh Poimboeuf (1):
static_call: Allow module use without exposing static_call_key

Juri Lelli (2):
sched/features: Fix hrtick reprogramming
sched/features: Distinguish between NORMAL and DEADLINE hrtick

Mel Gorman (4):
sched/fair: Remove SIS_AVG_CPU
sched/fair: Move avg_scan_cost calculations under SIS_PROP
sched/fair: Remove select_idle_smt()
sched/fair: Merge select_idle_core/cpu()

Michal Hocko (1):

Peter Oskolkov (1):
sched: Correctly sort struct predeclarations

Peter Zijlstra (13):
sched: Add schedutil overview
rbtree: Add generic add and find helpers
rbtree, sched/fair: Use rb_add_cached()
rbtree, sched/deadline: Use rb_add_cached()
rbtree, perf: Use new rbtree helpers
rbtree, uprobes: Use rbtree helpers
rbtree, rtmutex: Use rb_add_cached()
rbtree, timerqueue: Use rb_add_cached()
static_call: Pull some static_call declarations to the type headers
static_call/x86: Add __static_call_return0()
sched: Add /debug/sched_preempt
sched,x86: Allow !PREEMPT_DYNAMIC

Peter Zijlstra (Intel) (4):
preempt/dynamic: Provide cond_resched() and might_resched() static calls
preempt/dynamic: Provide preempt_schedule[_notrace]() static calls
preempt/dynamic: Provide irqentry_exit_cond_resched() static call
preempt/dynamic: Support dynamic preempt with preempt= boot option

Qais Yousef (1):
sched/eas: Don't update misfit status if the task is pinned

Sebastian Andrzej Siewior (1):
smp: Process pending softirqs in flush_smp_call_function_from_idle()

Sven Schnelle (1):
uprobes: (Re)add missing get_uprobe() in __find_uprobe()

Valentin Schneider (1):
sched/topology: Make sched_init_numa() use a set for the deduplicating sort

Vincent Guittot (3):
sched/fair: Skip idle cfs_rq
sched/fair: Don't set LBF_ALL_PINNED unnecessarily
sched/fair: Reduce cases for active balance

Viresh Kumar (3):
sched/core: Move schedutil_cpu_util() to core.c
sched/core: Rename schedutil_cpu_util() and allow rest of the kernel to use it
thermal: cpufreq_cooling: Reuse sched_cpu_util() for SMP platforms

Xuewen Yan (1):
sched/fair: Avoid stale CPU util_est value for schedutil in task dequeue

Yue Hu (1):
init/Kconfig: Correct thermal pressure help text

Documentation/admin-guide/kernel-parameters.txt | 7 +
Documentation/scheduler/schedutil.txt | 169 +++++++++++
arch/Kconfig | 9 +
arch/powerpc/platforms/cell/spufs/sched.c | 2 +-
arch/x86/Kconfig | 1 +
arch/x86/include/asm/preempt.h | 48 +++-
arch/x86/include/asm/static_call.h | 7 +
arch/x86/kernel/static_call.c | 17 +-
arch/x86/kvm/x86.c | 1 +
drivers/thermal/cpufreq_cooling.c | 69 ++++-
include/asm-generic/vmlinux.lds.h | 5 +-
include/linux/cgroup.h | 4 +-
include/linux/entry-common.h | 4 +
include/linux/entry-kvm.h | 14 +
include/linux/kernel.h | 23 +-
include/linux/rbtree.h | 206 +++++++++++++-
include/linux/rcupdate.h | 2 +
include/linux/sched.h | 34 ++-
include/linux/sched/prio.h | 18 +-
include/linux/static_call.h | 77 +++--
include/linux/static_call_types.h | 50 ++++
include/linux/topology.h | 1 +
init/Kconfig | 2 +-
kernel/Kconfig.preempt | 19 ++
kernel/entry/common.c | 17 +-
kernel/events/core.c | 195 ++++++-------
kernel/events/uprobes.c | 80 +++---
kernel/locking/rtmutex.c | 54 ++--
kernel/rcu/tree.c | 53 +++-
kernel/rcu/tree.h | 2 +-
kernel/rcu/tree_plugin.h | 31 +-
kernel/sched/core.c | 357 ++++++++++++++++++++++--
kernel/sched/cpufreq_schedutil.c | 108 +------
kernel/sched/deadline.c | 94 +++----
kernel/sched/debug.c | 2 +-
kernel/sched/fair.c | 322 +++++++++++----------
kernel/sched/features.h | 2 +-
kernel/sched/idle.c | 1 +
kernel/sched/rt.c | 2 +-
kernel/sched/sched.h | 51 ++--
kernel/sched/topology.c | 99 ++++---
kernel/smp.c | 4 +
kernel/static_call.c | 60 +++-
lib/timerqueue.c | 28 +-
tools/include/linux/rbtree.h | 192 ++++++++++++-
tools/include/linux/static_call_types.h | 50 ++++
tools/objtool/check.c | 17 +-
tools/objtool/elf.c | 73 +----
48 files changed, 1898 insertions(+), 785 deletions(-)
create mode 100644 Documentation/scheduler/schedutil.txt