1、调试
echo N > /sys/module/printk/parameters/console_suspend
echo 1 > /sys/power/pm_print_times
打印出每个设备唤醒的耗时」
要优化的话，就要这样debug了，看那边时间长，然后去优化对应模块咯
diff --git a/init/main.c b/init/main.c
index acbb01c..39a3b89 100755
--- a/init/main.c
+++ b/init/main.c
@ -652,7 +652,7 @ static void __init do_ctors(void)
#endif
}
-int initcall_debug;
+int initcall_debug=1;
core_param(initcall_debug, initcall_debug, bool, 0644);
2、日志对比
12-07 07:40:15.930 2717 2787 W System.err: at java.lang.Thread.run(Thread.java:761)
12-07 07:40:15.930 2717 2787 W System.err: Caused by: java.lang.ClassNotFoundException: Didn't find class "com.baidu.cloudsdk.common.http.RequestParams" on path: DexPathList[[zip file "/data/app/com.baidu.appsearch-2/base.apk"],nativeLibraryDirectories=[/data/app/com.baidu.appsearch-2/lib/arm, /system/fake-libs, /data/app/com.baidu.appsearch-2/base.apk!/lib/armeabi, /system/lib, /vendor/lib]]
12-07 07:40:15.930 2717 2787 W System.err: at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
12-07 07:40:15.930 2717 2787 W System.err: at java.lang.ClassLoader.loadClass(ClassLoader.java:380)
12-07 07:40:15.930 2717 2787 W System.err: at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
12-07 07:40:15.930 2717 2787 W System.err: ... 10 more
12-07 07:40:15.952 585 684 D SurfaceControl: Excessive delay in setPowerMode(): 139ms
12-07 07:40:15.952 585 684 E Lights Hal: write_int failed to open /sys/class/backlight/rk28_bl/brightness
12-07 07:40:15.958 585 684 E Lights Hal: write_int failed to open /sys/class/backlight/rk28_bl/brightness
12-07 07:40:15.982 585 684 E Lights Hal: write_int failed to open /sys/class/backlight/rk28_bl/brightness
12-07 07:40:15.997 585 684 E Lights Hal: write_int failed to open /sys/class/backlight/rk28_bl/brightness
12-07 07:40:16.014 585 684 E Lights Hal: write_int failed to open /sys/class/backlight/rk28_bl/brightness
这个是RK3399 的日志，setPowerMode 这里是 139ms
明显比RK3288 快的多得多！参考
Initcall Debug
Introduction
Passing the option "initcall_debug" on the kernel command line will cause timing information to be printed to the console for each initcall. initcalls are used to initialize statically linked kernel drivers and subsystems and contribute a significant amount of time to the Linux boot process. The output looks like this:
calling ipc_init+0x0/0x28 @ 1 msgmni has been set to 42 initcall ipc_init+0x0/0x28 returned 0 after 1872 usecs
You can use 'dmesg' to see the messages after the kernel has booted. With a short 'sed' script, you can reorder the final 'timing' line, and sort the initcalls numerically by duration. Here is a command to do this:
dmesg -s 128000 | grep "initcall" | sed "s/\(.*\)after\(.*\)/\2 \1/g" | sort -n
Sample output
Here is some sample output from the above command sequence. This was on an old X86-based desktop system. Printk Times was turned on (hence the extra timestamp on each line.)
24 msecs [ 2.237177] initcall acpi_button_init+0x0/0x51 returned 0
28 msecs [ 0.763503] initcall init_acpi_pm_clocksource+0x0/0x16c returned 0
32 msecs [ 0.348241] initcall acpi_pci_link_init+0x0/0x43 returned 0
33 msecs [ 0.919004] initcall inet_init+0x0/0x1c7 returned 0
33 msecs [ 5.282722] initcall psmouse_init+0x0/0x5e returned 0
54 msecs [ 2.979825] initcall e100_init_module+0x0/0x4d returned 0
71 msecs [ 0.650325] initcall pnp_system_init+0x0/0xf returned 0
91 msecs [ 0.872402] initcall pcibios_assign_resources+0x0/0x85 returned 0
187 msecs [ 4.369187] initcall ehci_hcd_init+0x0/0x70 returned 0
245 msecs [ 2.777161] initcall serial8250_init+0x0/0x100 returned 0
673 msecs [ 5.098052] initcall uhci_hcd_init+0x0/0xc1 returned 0
830 msecs [ 4.067279] initcall piix_init+0x0/0x27 returned 0
1490 msecs [ 8.290606] initcall ip_auto_config+0x0/0xd70 returned 0Notes
Using initcall_debug increases the amount of messages produced by the kernel during system boot. It's a good idea to increase the printk log buffer size to avoid overflowing the log buffer. To do this, increase the value of CONFIG_LOG_BUF_SHIFT from 14 to 18. This increases the log buffer from the default size of 16k to 256K.
You will need to enable CONFIG_PRINTK_TIME and CONFIG_KALLSYMS in your kernel configuration for this to work correctly. The first option displays printk timings and the second option ensures that function names are printed rather than memory addresses.
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