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2aaf709a51
linux-next/kernel
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Rafael J. Wysocki 2aaf709a51 sched: idle: Do not stop the tick upfront in the idle loop 
Push the decision whether or not to stop the tick somewhat deeper
into the idle loop.

Stopping the tick upfront leads to unpleasant outcomes in case the
idle governor doesn't agree with the nohz code on the duration of the
upcoming idle period.  Specifically, if the tick has been stopped and
the idle governor predicts short idle, the situation is bad regardless
of whether or not the prediction is accurate.  If it is accurate, the
tick has been stopped unnecessarily which means excessive overhead.
If it is not accurate, the CPU is likely to spend too much time in
the (shallow, because short idle has been predicted) idle state
selected by the governor [1].

As the first step towards addressing this problem, change the code
to make the tick stopping decision inside of the loop in do_idle().
In particular, do not stop the tick in the cpu_idle_poll() code path.
Also don't do that in tick_nohz_irq_exit() which doesn't really have
enough information on whether or not to stop the tick.

Link: https://marc.info/?l=linux-pm&m=150116085925208&w=2 # [1]
Link: https://tu-dresden.de/zih/forschung/ressourcen/dateien/projekte/haec/powernightmares.pdf
Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2018-04-05 19:01:14 +02:00
..
bpf bpf: skip unnecessary capability check 2018-03-20 23:50:39 +01:00
cgroup cgroup: fix rule checking for threaded mode switching 2018-02-21 11:39:22 -08:00
configs KVM changes for 4.16 2018-02-10 13:16:35 -08:00
debug signal: Simplify and fix kdb_send_sig 2018-01-03 18:01:08 -06:00
events perf/x86/pt, coresight: Clean up address filter structure 2018-03-29 16:07:22 +02:00
gcov License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq genirq/matrix: Handle CPU offlining proper 2018-02-22 22:05:43 +01:00
livepatch Merge branch 'for-4.16/remove-immediate' into for-linus 2018-01-31 16:36:38 +01:00
locking locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches 2018-03-31 07:30:50 +02:00
power Power management updates for 4.17-rc1 2018-04-03 10:45:39 -07:00
printk Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2018-03-01 10:06:39 -08:00
rcu Merge branches 'fixes.2018.02.23a', 'srcu.2018.02.20a' and 'torture.2018.02.20a' into HEAD 2018-02-23 15:15:41 -08:00
sched sched: idle: Do not stop the tick upfront in the idle loop 2018-04-05 19:01:14 +02:00
time sched: idle: Do not stop the tick upfront in the idle loop 2018-04-05 19:01:14 +02:00
trace Merge branch 'perf/urgent' into perf/core 2018-03-29 16:03:48 +02:00
.gitignore
acct.c kernel/acct.c: fix the acct->needcheck check in check_free_space() 2018-01-04 16:45:09 -08:00
async.c kernel/async.c: revert "async: simplify lowest_in_progress()" 2018-02-06 18:32:44 -08:00
audit_fsnotify.c
audit_tree.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-11-14 14:08:20 -08:00
audit_watch.c audit/stable-4.13 PR 20170816 2017-08-16 16:48:34 -07:00
audit.c Audit: remove unused audit_log_secctx function 2017-11-10 16:08:47 -05:00
audit.h audit/stable-4.15 PR 20171113 2017-11-15 13:28:48 -08:00
auditfilter.c audit: filter PATH records keyed on filesystem magic 2017-11-10 16:08:56 -05:00
auditsc.c audit/stable-4.15 PR 20171113 2017-11-15 13:28:48 -08:00
backtracetest.c
bounds.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
capability.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat.c mm: add kernel_move_pages() helper, move compat syscall to mm/migrate.c 2018-04-02 20:15:32 +02:00
configs.c
context_tracking.c
cpu_pm.c PM / CPU: replace raw_notifier with atomic_notifier 2017-07-31 13:09:49 +02:00
cpu.c cpu/hotplug: Fix unused function warning 2018-03-15 20:34:40 +01:00
crash_core.c kdump: write correct address of mem_section into vmcoreinfo 2018-01-13 10:42:48 -08:00
crash_dump.c
cred.c
delayacct.c delayacct: Account blkio completion on the correct task 2018-01-16 03:29:36 +01:00
dma.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
elfcore.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
exec_domain.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
exit.c kernel: use kernel_wait4() instead of sys_wait4() 2018-04-02 20:14:51 +02:00
extable.c extable: Make init_kernel_text() global 2018-02-21 16:54:06 +01:00
fail_function.c error-injection: Fix to prohibit jump optimization 2018-03-12 16:16:00 +01:00
fork.c kernel: add ksys_unshare() helper; remove in-kernel calls to sys_unshare() 2018-04-02 20:16:06 +02:00
freezer.c
futex_compat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
futex.c pids: introduce find_get_task_by_vpid() helper 2018-02-06 18:32:46 -08:00
groups.c kernel: make groups_sort calling a responsibility group_info allocators 2017-12-14 16:00:49 -08:00
hung_task.c
irq_work.c irq/work: Improve the flag definitions 2018-01-08 19:43:15 +01:00
jump_label.c jump_label: Disable jump labels in __exit code 2018-03-20 08:57:17 +01:00
kallsyms.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2018-02-01 13:36:15 -08:00
kcmp.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: detect double association with a single task 2018-02-06 18:32:46 -08:00
kexec_core.c x86/mm, kexec: Allow kexec to be used with SME 2017-07-18 11:38:04 +02:00
kexec_file.c resource: Provide resource struct in resource walk callback 2017-11-07 15:35:57 +01:00
kexec_internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kexec.c kexec: call do_kexec_load() in compat syscall directly 2018-04-02 20:15:01 +02:00
kmod.c kmod: move #ifdef CONFIG_MODULES wrapper to Makefile 2017-09-08 18:26:51 -07:00
kprobes.c kprobes: Propagate error from disarm_kprobe_ftrace() 2018-02-16 09:12:58 +01:00
ksysfs.c kexec: move vmcoreinfo out of the kernel's .bss section 2017-07-12 16:25:59 -07:00
kthread.c treewide: Remove TIMER_FUNC_TYPE and TIMER_DATA_TYPE casts 2017-11-21 16:35:54 -08:00
latencytop.c
Makefile error-injection: Support fault injection framework 2018-01-12 17:33:38 -08:00
memremap.c kernel/memremap: Remove stale devres_free() call 2018-03-06 10:58:54 -08:00
module_signing.c
module-internal.h
module.c arch: remove obsolete architecture ports 2018-04-02 20:20:12 -07:00
notifier.c
nsproxy.c
padata.c padata: add SPDX identifier 2018-01-05 18:43:00 +11:00
panic.c Merge branch 'core-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-02 09:08:26 -07:00
params.c kernel/params.c: improve STANDARD_PARAM_DEF readability 2017-10-03 17:54:26 -07:00
pid_namespace.c kernel: use kernel_wait4() instead of sys_wait4() 2018-04-02 20:14:51 +02:00
pid.c pids: introduce find_get_task_by_vpid() helper 2018-02-06 18:32:46 -08:00
profile.c
ptrace.c pids: introduce find_get_task_by_vpid() helper 2018-02-06 18:32:46 -08:00
range.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
reboot.c kernel/reboot.c: add devm_register_reboot_notifier() 2017-11-17 16:10:04 -08:00
relay.c kernel/relay.c: limit kmalloc size to KMALLOC_MAX_SIZE 2018-02-21 15:35:43 -08:00
resource.c Merge branch 'akpm' (patches from Andrew) 2018-02-06 22:15:42 -08:00
seccomp.c - Fix seccomp GET_METADATA to deal with field sizes correctly (Tycho Andersen) 2018-02-22 10:50:24 -08:00
signal.c kernel: add do_compat_sigaltstack() helper; remove in-kernel call to compat syscall 2018-04-02 20:15:29 +02:00
smp.c smp/core: Use lockdep to assert IRQs are disabled/enabled 2017-11-08 11:13:50 +01:00
smpboot.c watchdog/core, powerpc: Lock cpus across reconfiguration 2017-10-04 10:53:54 +02:00
smpboot.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
softirq.c softirq: Eliminate cond_resched_rcu_qs() in favor of cond_resched() 2017-12-04 10:28:58 -08:00
stacktrace.c
stop_machine.c
sys_ni.c kernel/sys_ni: remove {sys_,sys_compat} from cond_syscall definitions 2018-04-02 20:16:20 +02:00
sys.c kernel: add ksys_setsid() helper; remove in-kernel call to sys_setsid() 2018-04-02 20:16:06 +02:00
sysctl_binary.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sysctl.c pipe: reject F_SETPIPE_SZ with size over UINT_MAX 2018-02-06 18:32:47 -08:00
task_work.c locking/barriers: Convert users of lockless_dereference() to READ_ONCE() 2017-12-17 13:57:15 +01:00
taskstats.c pids: introduce find_get_task_by_vpid() helper 2018-02-06 18:32:46 -08:00
test_kprobes.c kprobes: Disable the jprobes test code 2017-10-20 11:02:54 +02:00
torture.c torture: Save a line in stutter_wait(): while -> for 2017-12-11 09:18:30 -08:00
tracepoint.c tracepoint: Remove smp_read_barrier_depends() from comment 2017-12-04 10:52:56 -08:00
tsacct.c
ucount.c
uid16.c fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers 2018-04-02 20:15:59 +02:00
uid16.h kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c 2018-04-02 20:15:30 +02:00
umh.c kernel: use kernel_wait4() instead of sys_wait4() 2018-04-02 20:14:51 +02:00
up.c smp: Avoid using two cache lines for struct call_single_data 2017-08-29 15:14:38 +02:00
user_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2017-11-16 12:20:15 -08:00
user-return-notifier.c
user.c efivarfs: Limit the rate for non-root to read files 2018-02-22 10:21:02 -08:00
utsname_sysctl.c
utsname.c
watchdog_hld.c Merge branch 'linus' into core/urgent, to pick up dependent commits 2017-11-04 08:53:04 +01:00
watchdog.c Merge branch 'linus' into sched/core, to pick up fixes 2017-11-08 10:17:15 +01:00
workqueue_internal.h Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2017-11-06 12:26:49 -08:00
workqueue.c Merge branch 'linus' into sched/core, to pick up fixes 2018-03-20 08:08:02 +01:00