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.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
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
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.c
cpu/hotplug: Fix unused function warning
2018-03-15 20:34:40 +01:00
cpu_pm.c
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.c
pids: introduce find_get_task_by_vpid() helper
2018-02-06 18:32:46 -08:00
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
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.c
kexec: call do_kexec_load() in compat syscall directly
2018-04-02 20:15:01 +02:00
kexec_core.c
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
kmod.c
kprobes.c
kprobes: Propagate error from disarm_kprobe_ftrace()
2018-02-16 09:12:58 +01:00
ksysfs.c
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-internal.h
module.c
arch: remove obsolete architecture ports
2018-04-02 20:20:12 -07:00
module_signing.c
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
pid.c
pids: introduce find_get_task_by_vpid() helper
2018-02-06 18:32:46 -08:00
pid_namespace.c
kernel: use kernel_wait4() instead of sys_wait4()
2018-04-02 20:14:51 +02:00
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
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.c
kernel: add ksys_setsid() helper; remove in-kernel call to sys_setsid()
2018-04-02 20:16:06 +02:00
sys_ni.c
kernel/sys_ni: remove {sys_,sys_compat} from cond_syscall definitions
2018-04-02 20:16:20 +02:00
sysctl.c
pipe: reject F_SETPIPE_SZ with size over UINT_MAX
2018-02-06 18:32:47 -08:00
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
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
user-return-notifier.c
user.c
efivarfs: Limit the rate for non-root to read files
2018-02-22 10:21:02 -08:00
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
utsname.c
utsname_sysctl.c
watchdog.c
Merge branch 'linus' into sched/core, to pick up fixes
2017-11-08 10:17:15 +01:00
watchdog_hld.c
Merge branch 'linus' into core/urgent, to pick up dependent commits
2017-11-04 08:53:04 +01:00
workqueue.c
Merge branch 'linus' into sched/core, to pick up fixes
2018-03-20 08:08:02 +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