Peter Zijlstra
6ccdc84b81
sched: Skip double execution of pick_next_task_fair()
...
Tim wrote:
"The current code will call pick_next_task_fair a second time in the
slow path if we did not pull any task in our first try. This is
really unnecessary as we already know no task can be pulled and it
doubles the delay for the cpu to enter idle.
We instrumented some network workloads and that saw that
pick_next_task_fair is frequently called twice before a cpu enters
idle. The call to pick_next_task_fair can add non trivial latency as
it calls load_balance which runs find_busiest_group on an hierarchy of
sched domains spanning the cpus for a large system. For some 4 socket
systems, we saw almost 0.25 msec spent per call of pick_next_task_fair
before a cpu can be idled."
Optimize the second call away for the common case and document the
dependency.
Reported-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Len Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/20140424100047.GP11096@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-05-07 11:51:35 +02:00
..
debug
mm: per-thread vma caching
2014-04-07 16:35:53 -07:00
events
Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm
2014-04-05 13:20:43 -07:00
gcov
gcov: reuse kbasename helper
2013-11-13 12:09:34 +09:00
irq
genirq: Export symbol no_action()
2014-03-22 11:33:09 +01:00
locking
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-04-16 16:35:18 -07:00
power
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
printk
printk: fix one circular lockdep warning about console_lock
2014-04-03 16:21:08 -07:00
rcu
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-03-31 11:21:19 -07:00
sched
sched: Skip double execution of pick_next_task_fair()
2014-05-07 11:51:35 +02:00
time
tick-sched: Check tick_nohz_enabled in tick_nohz_switch_to_nohz()
2014-04-15 20:26:58 +02:00
trace
This contains two fixes.
2014-04-18 10:16:43 -07:00
.gitignore
Ignore generated file kernel/x509_certificate_list
2013-12-10 18:21:34 +00:00
acct.c
async.c
audit.c
Merge git://git.infradead.org/users/eparis/audit
2014-04-12 12:38:53 -07:00
audit.h
audit: Use struct net not pid_t to remember the network namespce to reply in
2014-03-20 10:10:53 -04:00
audit_tree.c
inotify: Fix reporting of cookies for inotify events
2014-02-18 11:17:17 +01:00
audit_watch.c
inotify: Fix reporting of cookies for inotify events
2014-02-18 11:17:17 +01:00
auditfilter.c
Merge git://git.infradead.org/users/eparis/audit
2014-04-12 12:38:53 -07:00
auditsc.c
Merge git://git.infradead.org/users/eparis/audit
2014-04-12 12:38:53 -07:00
backtracetest.c
bounds.c
mm: do not allocate page->ptl dynamically, if spinlock_t fits to long
2013-12-20 12:25:45 -08:00
capability.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
2014-04-03 09:26:18 -07:00
cgroup.c
cgroup: newly created dirs and files should be owned by the creator
2014-04-07 16:44:47 -04:00
cgroup_freezer.c
cgroup: drop const from @buffer of cftype->write_string()
2014-03-19 10:23:54 -04:00
compat.c
Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-04-02 12:51:41 -07:00
configs.c
context_tracking.c
context_tracking: Wrap static key check into more intuitive function name
2013-12-02 20:43:14 +01:00
cpu.c
CPU hotplug: Provide lockless versions of callback registration functions
2014-03-20 13:43:40 +01:00
cpu_pm.c
cpuset.c
Merge branch 'akpm' (incoming from Andrew)
2014-04-03 16:22:16 -07:00
crash_dump.c
cred.c
delayacct.c
kernel/delayacct.c: remove redundant checking in __delayacct_add_tsk()
2013-11-13 12:09:12 +09:00
dma.c
elfcore.c
switch elf_core_write_extra_phdrs() to dump_emit()
2013-11-09 00:16:23 -05:00
exec_domain.c
exit.c
wait: WSTOPPED|WCONTINUED doesn't work if a zombie leader is traced by another process
2014-04-07 16:36:06 -07:00
extable.c
asmlinkage: Make main_extable_sort_needed visible
2014-02-13 18:13:22 -08:00
fork.c
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
freezer.c
libata, freezer: avoid block device removal while system is frozen
2013-12-19 13:50:32 -05:00
futex.c
futex: update documentation for ordering guarantees
2014-04-12 17:57:51 -07:00
futex_compat.c
compat: Get rid of (get|put)_compat_time(val|spec)
2014-02-02 14:09:12 -08:00
groups.c
kernel/groups.c: remove return value of set_groups
2014-04-03 16:21:05 -07:00
hrtimer.c
timer: Remove code redundancy while calling get_nohz_timer_target()
2014-03-20 12:35:46 +01:00
hung_task.c
kernel: audit/fix non-modular users of module_init in core code
2014-04-03 16:21:07 -07:00
irq_work.c
perf/x86: Warn to early_printk() in case irq_work is too slow
2014-02-21 21:49:07 +01:00
itimer.c
jump_label.c
static_key: WARN on usage before jump_label_init was called
2013-10-19 19:45:35 -04:00
kallsyms.c
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
kernel: remove CONFIG_USE_GENERIC_SMP_HELPERS
2013-11-15 09:32:22 +09:00
Kconfig.locks
Kconfig.preempt
kexec.c
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
kmod.c
execve: use 'struct filename *' for executable name passing
2014-02-05 12:54:53 -08:00
kprobes.c
kprobes: use KSYM_NAME_LEN to size identifier buffers
2013-11-13 12:09:26 +09:00
ksysfs.c
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
kthread.c
kthread: ensure locality of task_struct allocations
2014-04-03 16:20:49 -07:00
latencytop.c
Makefile
Merge branch 'x86-asmlinkage-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-03-31 14:13:25 -07:00
module-internal.h
KEYS: Separate the kernel signature checking keyring from module signing
2013-09-25 17:17:01 +01:00
module.c
modules: use raw_cpu_write for initialization of per cpu refcount.
2014-04-07 16:36:14 -07:00
module_signing.c
keys: change asymmetric keys to use common hash definitions
2013-10-25 17:15:18 -04:00
notifier.c
notifier: Substitute rcu_access_pointer() for rcu_dereference_raw()
2014-02-26 06:35:13 -08:00
nsproxy.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
2013-09-07 14:35:32 -07:00
padata.c
padata: Fix wrong usage of rcu_dereference()
2013-12-05 21:28:42 +08:00
panic.c
kernel/panic.c: display reason at end + pr_emerg
2014-04-07 16:36:08 -07:00
params.c
params: improve standard definitions
2013-12-04 14:09:46 +10:30
pid.c
pidns: fix free_pid() to handle the first fork failure
2013-09-30 14:31:03 -07:00
pid_namespace.c
pid_namespace: pidns_get() should check task_active_pid_ns() != NULL
2014-04-02 16:20:21 -07:00
posix-cpu-timers.c
posix-timers: Convert abuses of BUG_ON to WARN_ON
2013-12-09 16:56:29 +01:00
posix-timers.c
profile.c
CPU hotplug notifiers registration fixes for 3.15-rc1
2014-04-07 14:55:46 -07:00
ptrace.c
kernel/compat: convert to COMPAT_SYSCALL_DEFINE
2014-03-06 15:35:10 +01:00
range.c
reboot.c
kexec: migrate to reboot cpu
2013-12-18 19:04:50 -08:00
relay.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2014-04-12 14:49:50 -07:00
res_counter.c
res_counter: remove interface for locked charging and uncharging
2014-04-07 16:35:54 -07:00
resource.c
kernel/resource.c: make reallocate_resource() static
2014-04-03 16:21:07 -07:00
seccomp.c
seccomp: fix memory leak on filter attach
2014-04-16 15:25:53 -04:00
signal.c
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
smp.c
smp: Rename __smp_call_function_single() to smp_call_function_single_async()
2014-02-24 14:47:15 -08:00
smpboot.c
smpboot.h
softirq.c
softirq: Add linux/irq.h to make it compile again
2014-03-19 11:28:14 +01:00
stacktrace.c
stop_machine.c
stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus()
2014-03-11 11:33:47 +01:00
sys.c
mm, thp: add VM_INIT_DEF_MASK and PRCTL_THP_DISABLE
2014-04-07 16:35:52 -07:00
sys_ni.c
fs, kernel: permit disabling the uselib syscall
2014-04-03 16:21:05 -07:00
sysctl.c
hung_task: check the value of "sysctl_hung_task_timeout_sec"
2014-04-07 16:36:07 -07:00
sysctl_binary.c
kernel/sysctl_binary.c: use scnprintf() instead of snprintf()
2013-11-13 12:09:33 +09:00
system_certificates.S
KEYS: correct alignment of system_certificate_list content in assembly file
2013-12-10 18:25:28 +00:00
system_keyring.c
KEYS: correct alignment of system_certificate_list content in assembly file
2013-12-10 18:25:28 +00:00
task_work.c
task_work: documentation
2013-09-11 15:58:27 -07:00
taskstats.c
genetlink: only pass array to genl_register_family_with_ops()
2013-11-19 16:39:05 -05:00
test_kprobes.c
time.c
timeconst.bc
timer.c
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-04-01 11:00:07 -07:00
torture.c
rcutorture: Gracefully handle NULL cleanup hooks
2014-02-23 09:04:39 -08:00
tracepoint.c
This includes the final patch to clean up and fix the issue with the
2014-04-12 13:06:10 -07:00
tsacct.c
uid16.c
userns: Kill nsown_capable it makes the wrong thing easy
2013-08-30 23:44:11 -07:00
up.c
smp: Rename __smp_call_function_single() to smp_call_function_single_async()
2014-02-24 14:47:15 -08:00
user-return-notifier.c
user.c
kernel: audit/fix non-modular users of module_init in core code
2014-04-03 16:21:07 -07:00
user_namespace.c
user namespace: fix incorrect memory barriers
2014-04-14 16:03:02 -07:00
utsname.c
userns: Kill nsown_capable it makes the wrong thing easy
2013-08-30 23:44:11 -07:00
utsname_sysctl.c
watchdog.c
kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()
2014-04-18 16:40:08 -07:00
workqueue.c
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-04-01 11:00:07 -07:00
workqueue_internal.h