Perf是Linux kernel自带的系统性能优化工具。Perf的优势在于与Linux Kernel的紧密结合，它可以最先应用到加入Kernel的new feature。pef可以用于查看热点函数，查看cashe miss的比率，从而帮助开发者来优化程序性能。
编译器：gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf.tar.xz
Linux Kernel: imx6Q 4.1.15
1）补丁
Makefile.perf添加WERROR=0支持
2）编译
make LDFLAGS=-static ARCH=arm CROSS_COMPILE=/home/jiujin/workbench/toolchain/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- DEBUG=1
CC tests/hists_cumulate.o
CC tests/python-use.o
CC tests/bp_signal.o
CC tests/bp_signal_overflow.o
CC tests/task-exit.o
CC tests/sw-clock.o
CC tests/mmap-thread-lookup.o
CC tests/thread-mg-share.o
CC tests/switch-tracking.o
CC tests/keep-tracking.o
CC tests/code-reading.o
CC tests/sample-parsing.o
CC tests/parse-no-sample-id-all.o
CC tests/kmod-path.o
LD tests/perf-in.o
CC perf.o
LD perf-in.o
LINK perf
/work/aosp/kernel_imx/tools/lib/traceevent/libtraceevent.a(libtraceevent-in.o): In function `load_plugin':
/work/aosp/kernel_imx/tools/lib/traceevent/event-plugin.c:304: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
libperf.a(libperf-in.o): In function `target__parse_uid':
/work/aosp/kernel_imx/tools/perf/util/target.c:79: warning: Using 'getpwnam_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/work/aosp/kernel_imx/tools/perf/util/target.c:91: warning: Using 'getpwuid_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
GEN perf-archive
GEN perf-with-kcore
3)
sabresd_6dq:/data # ./perf top
Cannot read kernel map
Segmentation fault
->>> echo 0 > /proc/sys/kernel/kptr_restrict
4)
sabresd_6dq:/data # ./perf top
[mac80211] with build id f31d71174e3e0ac590852c07a0a1e9c79f219752 not found, continuing without symbols
PerfTop: 1563 irqs/sec kernel:93.7% exact: 0.0% [4000Hz cycles], (all, 2 CPUs)
-------------------------------------------------------------------------------
40.77% [kernel] [k] cpuidle_enter_state
8.96% [kernel] [k] radix_tree_lookup
7.83% [kernel] [k] __do_softirq
7.78% [kernel] [k] _raw_spin_unlock_irqrestore
7.55% [kernel] [k] _raw_spin_unlock_irq
2.56% [kernel] [k] preempt_count_add
2.56% [kernel] [k] __timer_delay
1.28% [kernel] [k] put_cpu_partial
1.28% [kernel] [k] irq_to_desc
1.28% [kernel] [k] rcu_process_callbacks
1.28% [kernel] [k] file_free_rcu
1.28% libc.so [.] 0x000489f0
1.28% [kernel] [k] tick_nohz_idle_enter
1.28% [kernel] [k] __netif_receive_skb
1.27% [kernel] [k] avc_lookup
1.25% boot.oat [.] 0x00591f04
1.25% libc.so [.] 0x00017592
1.25% [kernel] [k] mix_pool_bytes