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54b933c6c9
linux/kernel/sched
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Cheng Jian 54b933c6c9 sched/idle: Micro-optimize the idle loop 
Move the loop-invariant calculation of 'cpu' in do_idle() out of the loop body,
because the current CPU is always constant.

This improves the generated code both on x86-64 and ARM64:

x86-64:

Before patch (execution in loop):
	864:       0f ae e8                lfence
	867:       65 8b 05 c2 38 f1 7e    mov %gs:0x7ef138c2(%rip),%eax
	86e:       89 c0                   mov %eax,%eax
	870:       48 0f a3 05 68 19 08    bt  %rax,0x1081968(%rip)
	877:	   01

After patch (execution in loop):
	872:       0f ae e8                lfence
	875:       4c 0f a3 25 63 19 08    bt  %r12,0x1081963(%rip)
	87c:       01

ARM64:

Before patch (execution in loop):
	c58:       d5033d9f        dsb     ld
	c5c:       d538d080        mrs     x0, tpidr_el1
	c60:       b8606a61        ldr     w1, [x19,x0]
	c64:       1100fc20        add     w0, w1, #0x3f
	c68:       7100003f        cmp     w1, #0x0
	c6c:       1a81b000        csel    w0, w0, w1, lt
	c70:       13067c00        asr     w0, w0, #6
	c74:       93407c00        sxtw    x0, w0
	c78:       f8607a80        ldr     x0, [x20,x0,lsl #3]
	c7c:       9ac12401        lsr     x1, x0, x1
	c80:       36000581        tbz     w1, #0, d30 <do_idle+0x128>

After patch (execution in loop):
	c84:       d5033d9f        dsb     ld
	c88:       f9400260        ldr     x0, [x19]
	c8c:       ea14001f        tst     x0, x20
	c90:       54000580        b.eq    d40 <do_idle+0x138>

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
[ Rewrote the title and the changelog. ]
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: huawei.libin@huawei.com
Cc: xiexiuqi@huawei.com
Link: http://lkml.kernel.org/r/1508930907-107755-1-git-send-email-cj.chengjian@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-26 08:31:29 +02:00
..
autogroup.c sched/autogroup: Fix error reporting printk text in autogroup_create() 2017-08-10 17:06:03 +02:00
autogroup.h sched/headers: Prepare for new header dependencies before moving code to <linux/sched/autogroup.h> 2017-03-02 08:42:28 +01:00
clock.c sched/clock: Fix early boot preempt assumption in __set_sched_clock_stable() 2017-05-24 09:10:00 +02:00
completion.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-04 11:52:29 -07:00
core.c sched/fair: Use reweight_entity() for set_user_nice() 2017-09-29 19:35:14 +02:00
cpuacct.c sched/cputime: Convert kcpustat to nsecs 2017-02-01 09:13:47 +01:00
cpuacct.h sched/cpuacct: Simplify the cpuacct code 2016-03-21 11:00:28 +01:00
cpudeadline.c sched/deadline: Change return value of cpudl_find() 2017-08-10 12:18:17 +02:00
cpudeadline.h sched/deadline: Split cpudl_set() into cpudl_set() and cpudl_clear() 2016-09-05 13:29:43 +02:00
cpufreq_schedutil.c Merge branch 'pm-cpufreq-sched' 2017-09-04 00:05:22 +02:00
cpufreq.c cpufreq / sched: Pass flags to cpufreq_update_util() 2016-08-16 22:14:55 +02:00
cpupri.c sched/cpupri: Don't re-initialize 'struct cpupri' 2017-08-10 12:18:14 +02:00
cpupri.h
cputime.c sched/cputime: Don't use smp_processor_id() in preemptible context 2017-07-14 10:27:15 +02:00
deadline.c sched/deadline: Rename __dl_clear() to __dl_sub() 2017-10-10 11:45:26 +02:00
debug.c sched/fair: Propagate an effective runnable_load_avg 2017-09-29 19:35:15 +02:00
fair.c sched/fair: Fix usage of find_idlest_group() when the local group is idlest 2017-10-10 11:45:36 +02:00
features.h sched/core: Address more wake_affine() regressions 2017-10-10 10:14:03 +02:00
idle_task.c sched/core: Add wrappers for lockdep_(un)pin_lock() 2017-01-14 11:29:30 +01:00
idle.c sched/idle: Micro-optimize the idle loop 2017-10-26 08:31:29 +02:00
loadavg.c sched/loadavg: Generalize "_idle" naming to "_nohz" 2017-06-22 11:30:01 +02:00
Makefile membarrier: Provide expedited private command 2017-08-17 07:28:05 -07:00
membarrier.c membarrier: Provide expedited private command 2017-08-17 07:28:05 -07:00
rt.c sched/rt: Simplify the IPI based RT balancing logic 2017-10-10 11:45:40 +02:00
sched-pelt.h sched/fair: Move the PELT constants into a generated header 2017-04-14 10:26:37 +02:00
sched.h sched/rt: Simplify the IPI based RT balancing logic 2017-10-10 11:45:40 +02:00
stats.c sched: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:37 -08:00
stats.h sched/headers: Move cputime functionality from <linux/sched.h> and <linux/cputime.h> into <linux/sched/cputime.h> 2017-03-03 01:45:22 +01:00
stop_task.c sched/core: Add wrappers for lockdep_(un)pin_lock() 2017-01-14 11:29:30 +01:00
swait.c sched/wait: Remove the lockless swait_active() check in swake_up*() 2017-08-10 12:28:53 +02:00
topology.c sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK 2017-10-24 11:47:25 +02:00
wait_bit.c sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming 2017-06-20 12:19:14 +02:00
wait.c sched/wait: Introduce wakeup boomark in wake_up_page_bit 2017-09-14 09:56:18 -07:00