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linux/arch/arm64/kernel
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Jisheng Zhang b5fda7ed5c arm64: cpuidle: make arm_cpuidle_suspend() a bit more efficient 
Currently, we check two pointers: cpu_ops and cpu_suspend on every idle
state entry. These pointers check can be avoided:

If cpu_ops has not been registered, arm_cpuidle_init() will return
-EOPNOTSUPP, so arm_cpuidle_suspend() will never have chance to
run. In other word, the cpu_ops check can be avoid.

Similarly, the cpu_suspend check could be avoided in this hot path by
moving it into arm_cpuidle_init().

I measured the 4096 * time from arm_cpuidle_suspend entry point to the
cpu_psci_cpu_suspend entry point. HW platform is Marvell BG4CT STB
board.

1. only one shell, no other process, hot-unplug secondary cpus, execute
the following cmd

while true
do
	sleep 0.2
done

before the patch: 1581220ns

after the patch: 1579630ns

reduced by 0.1%

2. only one shell, no other process, hot-unplug secondary cpus, execute
the following cmd

while true
do
	md5sum /tmp/testfile
	sleep 0.2
done

NOTE: the testfile size should be larger than L1+L2 cache size

before the patch: 1961960ns
after the patch: 1912500ns

reduced by 2.5%

So the more complex the system load, the bigger the improvement.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-04-13 14:49:23 +01:00
..
vdso arm64: vdso: Mark vDSO code as read-only 2016-02-16 18:20:23 +00:00
.gitignore arm64: Build infrastructure 2012-09-17 13:42:21 +01:00
acpi_parking_protocol.c arm64: kernel: acpi: fix ioremap in ACPI parking protocol cpu_postboot 2016-02-26 15:39:52 +00:00
acpi.c Power management and ACPI updates for v4.4-rc1 2015-11-04 18:10:13 -08:00
alternative.c arm64: mm: fold alternatives into .init 2015-12-10 17:36:08 +00:00
arm64ksyms.c ARM: 8480/2: arm64: add implementation for arm-smccc 2016-01-04 16:24:45 +00:00
armv8_deprecated.c arm64: switch to relative exception tables 2016-02-24 14:57:26 +00:00
asm-offsets.c arm64 updates for 4.6: 2016-03-17 20:03:47 -07:00
cacheinfo.c arm64: kernel: add support for cpu cache information 2015-01-15 11:55:07 +00:00
cpu_errata.c arm64: Add workaround for Cavium erratum 27456 2016-02-26 15:14:27 +00:00
cpu_ops.c arm64: kernel: implement ACPI parking protocol 2016-02-16 15:12:32 +00:00
cpufeature.c arm64: cpufeature: append additional id_aa64mmfr2 fields to cpufeature 2016-04-13 14:49:23 +01:00
cpuidle.c arm64: cpuidle: make arm_cpuidle_suspend() a bit more efficient 2016-04-13 14:49:23 +01:00
cpuinfo.c arm64: make mrs_s prefixing implicit in read_cpuid 2016-03-04 14:12:46 +00:00
debug-monitors.c arm64 updates for 4.6: 2016-03-17 20:03:47 -07:00
efi-entry.S arm64: efi: add missing frame pointer assignment 2016-03-04 18:12:23 +00:00
efi.c arm64/efi: refactor EFI init and runtime code for reuse by 32-bit ARM 2015-12-09 16:57:23 +00:00
entry32.S arm64: entry32: remove pointless register assignment 2015-07-10 16:47:13 +01:00
entry-fpsimd.S arm64: fpsimd: fix a typo in fpsimd_save_partial_state ENDPROC 2014-07-31 11:42:42 +01:00
entry-ftrace.S arm64: ftrace: fix function_graph tracer panic 2015-10-02 11:12:56 +01:00
entry.S arm64/kernel: fix incorrect EL0 check in inv_entry macro 2016-03-21 12:05:34 +00:00
fpsimd.c arm64: Fix misspellings in comments. 2016-03-04 18:19:17 +00:00
ftrace.c arm64: ftrace: modify a stack frame in a safe way 2015-12-21 17:26:01 +00:00
head.S 2nd set of arm64 updates for 4.6: 2016-03-24 19:13:59 -07:00
hw_breakpoint.c arm64: Fix missing #include in hw_breakpoint.c 2015-10-12 12:10:53 +01:00
hyp-stub.S irqchip: gic-v3: Initial support for GICv3 2014-07-08 22:11:47 +00:00
image.h arm64 updates for 4.6: 2016-03-17 20:03:47 -07:00
insn.c arm64: insn: remove BUG_ON from codegen 2016-01-17 19:15:26 -05:00
io.c arm64: optimize memcpy_{from,to}io() and memset_io() 2014-11-06 17:25:27 +00:00
irq.c arm64: remove irq_count and do_softirq_own_stack() 2015-12-21 17:26:01 +00:00
jump_label.c jump_label: Rename JUMP_LABEL_{EN,DIS}ABLE to JUMP_LABEL_{JMP,NOP} 2015-08-03 11:34:12 +02:00
kaslr.c arm64: kaslr: randomize the linear region 2016-02-24 14:57:27 +00:00
kgdb.c arm64: Fix misspellings in comments. 2016-03-04 18:19:17 +00:00
kuser32.S arm64: Add __NR_* definitions for compat syscalls 2014-07-10 11:02:40 +01:00
Makefile arm64: add support for kernel ASLR 2016-02-24 14:57:27 +00:00
module-plts.c arm64: add support for module PLTs 2016-02-24 14:57:24 +00:00
module.c arm64: add support for kernel ASLR 2016-02-24 14:57:27 +00:00
module.lds arm64: add support for module PLTs 2016-02-24 14:57:24 +00:00
paravirt.c arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops 2015-12-21 14:40:54 +00:00
pci.c ARM64: PCI: Remove generated include of asm-generic/pci-bridge.h 2016-02-05 16:29:12 -06:00
perf_callchain.c arm64: ftrace: fix a stack tracer's output under function graph tracer 2015-12-21 17:26:02 +00:00
perf_event.c arm64: perf: Move PMU register related defines to asm/perf_event.h 2016-03-29 16:04:57 +01:00
perf_regs.c perf: Move task_pt_regs sampling into arch code 2015-01-09 11:12:28 +01:00
process.c arm64: Remove the get_thread_info() function 2016-02-18 17:27:05 +00:00
psci.c ARM: 8511/1: ARM64: kernel: PSCI: move PSCI idle management code to drivers/firmware 2016-02-11 15:33:38 +00:00
ptrace.c arm64: Rework valid_user_regs 2016-03-02 15:49:28 +00:00
return_address.c arm64: ftrace: fix a stack tracer's output under function graph tracer 2015-12-21 17:26:02 +00:00
setup.c arm64 updates for 4.6: 2016-03-17 20:03:47 -07:00
signal32.c arm64: Fix misspellings in comments. 2016-03-04 18:19:17 +00:00
signal.c arm64: Rework valid_user_regs 2016-03-02 15:49:28 +00:00
sleep.S arm64: kasan: clear stale stack poison 2016-03-09 15:43:42 -08:00
smccc-call.S ARM: 8480/2: arm64: add implementation for arm-smccc 2016-01-04 16:24:45 +00:00
smp_spin_table.c ARM64: kernel: make cpu_ops hooks DT agnostic 2015-05-19 16:09:29 +01:00
smp.c arm64 updates for 4.6: 2016-03-17 20:03:47 -07:00
stacktrace.c arm64: make irq_stack_ptr more robust 2016-02-12 15:53:51 +00:00
suspend.c arm64: unify idmap removal 2016-02-16 15:10:44 +00:00
sys32.c arm64: fix implementation of mmap2 compat syscall 2015-03-19 10:43:51 +00:00
sys_compat.c arm64: compat: align cacheflush syscall with arch/arm 2014-12-01 13:31:12 +00:00
sys.c arm64: make sys_call_table const 2015-01-27 09:38:08 +00:00
time.c arm64: ftrace: fix a stack tracer's output under function graph tracer 2015-12-21 17:26:02 +00:00
topology.c arm64: kernel: remove non-legit DT warnings when booting using ACPI 2015-07-27 11:08:41 +01:00
trace-events-emulation.h arm64: Trace emulation of AArch32 legacy instructions 2014-11-20 16:35:02 +00:00
traps.c arm64: make irq_stack_ptr more robust 2016-02-12 15:53:51 +00:00
vdso.c arm64: VDSO: fix coarse clock monotonicity regression 2015-08-10 15:37:45 +01:00
vmlinux.lds.S arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00