Introduction
There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know.
——Donald Rumsfeld, Former U.S. Secretary of Defense, February 12, 2002
Overview
System performance is the study of the performance of the entire computer system, including major hardware components and software components. Understandably, this is a very broad topic, and only by deeply understanding the relationships between various components can one avoid missing the forest for the trees. Performance issues can arise from anywhere, including places in the system that you may not have checked (unknown unknowns).
The typical goal of system performance optimization is to improve the end-user experience by reducing latency and lowering computational costs. Optimizing system cold boot time is one aspect of performance optimization, and while it may not occur frequently in end-user scenarios, why should we still pursue it? This leads us to the trilogy of thinking: what, why, and how. Optimizing cold boot time means minimizing the time the system takes during the startup process, so why do we do this? For car users, cold booting is not common because most of the time the system wakes from sleep and does not undergo a complete power-on startup process. Just because something happens infrequently does not mean it won’t happen; when it does occur, you can make it better. This is the significance of optimizing cold boot time. If you optimize a 5-second startup time, it means reducing the driver’s 5 seconds of waiting time (the driver may need to wait for the system to start to navigate back to a long-lost hometown, and the road is too far to remember the way home
). If it’s 5 seconds for one person, what about 300,000 people (if a car model sells 300,000 units, that’s already quite good). Now that we’ve discussed what and why, let’s explore how to do it. Let’s go!
System Cold Boot Optimization – Methodology
Methodology is how we understand cold boot duration and the methods to optimize cold boot time. Without a methodology, our investigation would turn into a fishing expedition: randomly trying things in hopes of achieving success. This approach is both time-consuming and ineffective, and it may also overlook important matters. Once you have a deep understanding of a theory through practice, you can describe it in simple terms, such as:
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Maximize the utilization of system resources (CPU & GPU & IO) to fully utilize resources;
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What can be done earlier, do it earlier; what can be delayed, do it later; what can be trimmed, trim it; what can be parallelized, parallelize it;
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The improvement of boot speed must not sacrifice system stability.
System Cold Boot Optimization – Tool Usage
To do a good job, one must first sharpen their tools.
AOSP itself provides many useful tools, let’s take a look.
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Using Scripts for Analysis
Code located at $AOSP/system/extras/boottime_tools/bootanalyze
First, use bugreportz -p to capture a bug report, then use bugreport_analyze.py for analysis. You can visually see the time taken for each startup stage in Android, and based on this, we can optimize accordingly.
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Using simpleperf to capture cold boot data
Refer to Google’s patches for specifics; understanding the why is just as important as understanding the how.
simpleperf is used to track CPU usage; its actual utility may not be significant but can serve as a learning reference.
https://android-review.googlesource.com/c/platform/system/extras/+/1950976.https://android-review.googlesource.com/c/platform/system/extras/+/1963689.https://android-review.googlesource.com/c/platform/system/sepolicy/+/1950977.-
Using logcat events to track
This provides a rough overview of the timing status of each major process, serving as a reference for fine-tuning optimizations.
console:/ # logcat -b events | grep -i boot_progress01-01 00:00:13.848 549 549 I boot_progress_start: 973001-01 00:00:16.266 549 549 I boot_progress_preload_start: 1214801-01 00:00:18.265 549 549 I boot_progress_preload_end: 1414701-01 00:00:19.449 1116 1116 I boot_progress_system_run: 1533101-01 00:00:20.521 1116 1116 I boot_progress_pms_start: 1640301-01 00:00:20.767 1116 1116 I boot_progress_pms_system_scan_start: 1664801-01 00:00:21.062 1116 1116 I boot_progress_pms_data_scan_start: 1694401-01 00:00:21.067 1116 1116 I boot_progress_pms_scan_end: 1694901-01 00:00:21.223 1116 1116 I boot_progress_pms_ready: 1710505-12 18:53:14.364 1116 1116 I boot_progress_ams_ready: 1878505-12 18:53:18.188 1116 1142 I boot_progress_enable_screen: 22609-
Using perfetto to capture the startup process trace
Taking init startup as an example, we can visually see the specific reasons for the time taken, based on which we can optimize.
Using system_server as an example, we can visually see the startup duration of each service, based on which we can optimize.
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Using bootprof to track bootloader and kernel timing
bootprof is a tool developed by Mediatek for instrumentation printing; we can learn from this for other platforms as well, and it is quite useful.
console:/ # cat /proc/bootprof ----------------------------------------0 BOOT PROF (unit:msec)---------------------------------------- 1794 : preloader 6670 : lk---------------------------------------- 3.044076 : ON (Threshold: 15ms) 67.891076 : 1-swapper/0 : initcall: of_platform_default_populate_init 29.992923ms 111.268691 : 1-swapper/0 : initcall: tracer_init_tracefs 26.218846ms 129.068384 : 1-swapper/0 : probe: probe=platform_drv_probe drv=pateo_gpio(0xffffff9b525afc80) 16.369461ms 129.093922 : 1-swapper/0 : initcall: gpio_power_init 16.604000ms 367.956384 : 1-swapper/0 : initcall: populate_rootfs 227.612077ms 1043.026463 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mt6577-uart(0xffffff9b52541d78) 655.779771ms 1047.885001 : 1-swapper/0 : initcall: mtk8250_platform_driver_init 660.785232ms 1083.230232 : 1-swapper/0 : probe: probe=platform_drv_probe drv=gpufreq(0xffffff9b52545ab0) 32.324615ms 1085.065309 : 1-swapper/0 : initcall: __mt_gpufreq_init 34.282846ms 1115.272001 : 1-swapper/0 : initcall: mtk_spi_driver_init 16.221769ms 1146.894848 : 1-swapper/0 : probe: probe=platform_drv_probe drv=Accdet_Driver(0xffffff9b5254ce10) 18.433462ms 1149.585001 : 1-swapper/0 : initcall: accdet_mod_init 21.386385ms 1198.660079 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mtk_clkbuf_driver(0xffffff9b52574f50) 19.946385ms 1200.354848 : 1-swapper/0 : initcall: mtk_clkbuf_driver_init 21.944692ms 1278.662233 : 1-swapper/0 : initcall: ISP_Init 63.668923ms 1692.988926 : 1-swapper/0 : probe: probe=platform_drv_probe drv=image_sensor(0xffffff9b5257a1e0) 380.002693ms 1694.780080 : 1-swapper/0 : initcall: imgsensor_init 382.919693ms 1753.994464 : 1-swapper/0 : initcall: disp_probe_1 35.409847ms 1786.621234 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mtkfb(0xffffff9b52596498) 30.687462ms 1791.018849 : 1-swapper/0 : initcall: mtkfb_init 35.915000ms 1897.658465 : 1-swapper/0 : initcall: init_perfmgr 90.587693ms 1996.535080 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mtk_mmdvfs_pmqos(0xffffff9b525a23c0) 96.115770ms 1999.156388 : 1-swapper/0 : initcall: mmdvfs_pmqos_init 99.041154ms 2100.770465 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mtk-thermal(0xffffff9b525a46c0) 92.930461ms 2102.705004 : 1-swapper/0 : initcall: tscpu_init 95.767385ms 2148.588388 : 1-swapper/0 : initcall: mt6358tsbuck1_init 29.006230ms 2181.734542 : 1-swapper/0 : initcall: mt6358tsbuck2_init 31.967000ms 2211.887773 : 1-swapper/0 : initcall: mt6358tsbuck3_init 28.982461ms 2252.484619 : 1-swapper/0 : initcall: VPU_INIT 18.516000ms 2395.483158 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mt-rtc(0xffffff9b525cdc08) 54.275692ms 2395.522466 : 1-swapper/0 : initcall: mtk_rtc_pdrv_init 54.884539ms 2394.672620 : 262-mtu3_thread : probe: probe=platform_drv_probe drv=xhci-mtk(0xffffff9b525bf340) 83.506154ms 2441.471466 : 1-swapper/0 : probe: probe=platform_drv_probe drv=battery(0xffffff9b525d6bc8) 44.903692ms 2481.346543 : 1-swapper/0 : initcall: battery_init 84.968308ms 2513.009312 : 1-swapper/0 : initcall: mt_msdc_init 18.985231ms 2541.665236 : 1-swapper/0 : initcall: cis_main_init 22.029615ms 2594.468082 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mt-soc-dl1-pcm(0xffffff9b5261e798) 32.551000ms 2597.565313 : 1-swapper/0 : initcall: mtk_soc_platform_init 36.386231ms 2681.636082 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mtk-audio(0xffffff9b52627810) 73.374154ms 2684.059082 : 1-swapper/0 : initcall: mt_soc_snd_init 75.883078ms 2748.485005 : 1-swapper/0 : initcall: tipc_init 16.255616ms 2791.259390 : 1-swapper/0 : initcall: pinctrl_mtk_debug_v2_init 16.227923ms 2867.720621 : 1-swapper/0 : probe: probe=platform_drv_probe drv=mt-cpufreq(0xffffff9b52567828) 63.925923ms 2869.433236 : 1-swapper/0 : initcall: _mt_cpufreq_pdrv_init 68.277923ms 2924.937236 : 1-swapper/0 : initcall: mt_spm_init 38.467615ms 3094.374468 : 1-swapper/0 : probe: probe=i2c_device_probe drv=ICM42607_ACCEL(0xffffff9b52582c30) 161.108077ms 3096.220621 : 1-swapper/0 : initcall: acc_init 163.068615ms 3180.307468 : 1-swapper/0 : Kernel_init_done 5857.348320 : 329-init : INIT:early-init 6635.633861 : 329-init : INIT:init 6680.954784 : 329-init : INIT:late-init 6724.796630 : 329-init : INIT:early-fs 6725.362169 : 329-init : INIT:fs 6732.352015 : 329-init : INIT:Mount_START 7409.806786 : 329-init : INIT:Mount_END 7506.673247 : 274-kworker/u16:2 : probe: probe=platform_drv_probe drv=xhci-mtk(0xffffff9b525bf340) 99.747000ms 7516.208401 : 329-init : INIT:post-fs 7722.876633 : 329-init : INIT:late-fs 7727.973325 : 329-init : INIT:Mount_START --late 8971.286559 : 329-init : INIT:Mount_END --late 9013.209943 : 381-binder:381_2 : vold:fbeEnable:START 9014.265020 : 381-binder:381_2 : vold:retrieveOrGenerateKey:START 9019.617943 : 381-binder:381_2 : vold:retrieveOrGenerateKey:END, rtn =1 9020.814789 : 381-binder:381_2 : vold:install_storage_key(device_key):START 9022.617559 : 381-binder:381_2 : vold:install_storage_key:END, rtn =1 9029.566559 : 381-binder:381_2 : vold:generateStorageKey(per_boot_key):START 9030.873943 : 381-binder:381_2 : vold:generateStorageKey:END, rtn =1 9032.019405 : 381-binder:381_2 : vold:install_storage_key(per_boot_key):START 9033.528713 : 381-binder:381_2 : vold:install_storage_key:END, rtn =1 9036.999405 : 381-binder:381_2 : vold:fbeEnable:END, rtn =1 9542.817021 : 381-binder:381_2 : vold:initUser0:START 9584.440714 : 381-binder:381_2 : vold:initUser0:END, rtn =1 9816.008945 : 329-init : INIT:post-fs-data 9939.744715 : 329-init : post-fs-data: on modem start 10560.260409 : 329-init : INIT:zygote-start 10564.873947 : 329-init : INIT:early-boot 10977.542871 : 329-init : INIT:boot 11009.869563 : 649-ccci_mdinit : ccci_md1: md_init srv start 11015.539410 : 652-ccci_mdinit : ccci_md3: md_init srv start 11300.854487 : 451-wmt_loader : probe: probe=platform_drv_probe drv=mtk_wmt(alarm_timer_handler [wmt_drv]) 50.083385ms 11800.660335 : 808-android.hardwar : EvsEnumeratorHw service is starting 11800.710488 : 808-android.hardwar : ##EvsEnumerator ctr + 11800.730488 : 808-android.hardwar : ##EvsEnumerator ctr - 11822.872412 : 808-android.hardwar : begin to registerAsService 11834.240412 : [email protected] : EvsEnumeratorHw IS READY. 11927.662873 : 543-zygote64 : boot_progress_start 12341.725874 : 329-init : probe: probe=platform_drv_probe drv=fm(mt_fm_dev_drv [fmradio_drv_mt6631]) 78.951154ms 12349.091413 : 329-init : initcall: init_module [fmradio_drv_mt6631] 101.158770ms 12639.316644 : 329-init : USB ready 13449.468415 : 543-main : Zygote:Preload Start 13460.199492 : 544-main : Zygote:Preload End 15326.278189 : 543-main : Zygote:Preload 16236 classes in 1749ms 15413.496651 : 543-main : Zygote:Preload 64 obtain resources in 43ms 15422.495112 : 543-main : Zygote:Preload 41 resources in 8ms 15664.622882 : 543-main : Zygote:Preload End 16354.456422 : 1093-system_server : Android:SysServerInit_START 17182.076424 : 1093-system_server : Android:PackageManagerService_Start 17411.809271 : 1093-system_server : Android:PMS_scan_START 17423.021579 : 1093-system_server : Android:PMS_scan_data:/product/overlay 17445.905579 : 1093-system_server : Android:PMS_scan_data:/vendor/overlay 17458.837348 : 1093-system_server : Android:PMS_scan_data:/system/framework 17475.739810 : 1093-system_server : Android:PMS_scan_data:/system/priv-app 17541.987425 : 1093-system_server : Android:PMS_scan_data:/system/app 17610.909041 : 1093-system_server : Android:PMS_scan_data:/vendor/priv-app 17622.846810 : 1093-system_server : Android:PMS_scan_data:/vendor/app 17653.638195 : 1093-system_server : Android:PMS_scan_data:/product/priv-app 17664.301887 : 1093-system_server : Android:PMS_scan_data:/product/app 17670.214887 : 1093-system_server : Android:PMS_scan_data:/system/system_ext/priv-app 17693.423118 : 1093-system_server : Android:PMS_scan_data:/system/system_ext/app 17704.339810 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.wifi/priv-app 17718.895426 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.wifi/app 17729.378272 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.uwb/priv-app 17734.117964 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.tethering/priv-app 17740.168656 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.tethering/app 17750.308041 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.permission/priv-app 17769.576426 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.ondevicepersonalization/app 17783.625349 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.mediaprovider/priv-app 17801.494580 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.extservices/priv-app 17813.263810 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.car.framework/priv-app 17824.753272 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.car.framework/app 17836.328964 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.btservices/app 17857.441580 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.adservices/priv-app 17867.973580 : 1093-system_server : Android:PMS_scan_data:/apex/com.android.adservices/app 17887.077041 : 1093-system_server : Android:PMS_scan_END 17932.220426 : 1093-system_server : PMS:reconcileAppsDataLI 18051.248426 : 1093-system_server : Android:PMS_READY 19662.871430 : 1093-system_server : AMS:systemReady 19685.941276 : 1093-system_server : AMS:AMS_READY 19867.188123 : 544-main : Zygote:Preload 16236 classes in 1476ms 19954.766585 : 1093-system_server : SystemServer:NetworkStatsService systemReady 19956.351200 : 544-main : Zygote:Preload 64 obtain resources in 57ms 19968.021585 : 544-main : Zygote:Preload 41 resources in 9ms 19972.374816 : 1093-system_server : SystemServer:ConnectivityService systemReady 19987.229969 : 1093-system_server : SystemServer:NetworkPolicyManagerServ systemReady 20224.980047 : 1127-ActivityManager : AP_Init:[service]:[com.android.car]:[{com.android.car/com.android.car.CarService}]:pid:1373:(PersistAP) 20351.732355 : 1093-system_server : SystemServer:PhaseThirdPartyAppsCanStart 20377.113663 : 1127-ActivityManager : AP_Init:[]:[WebViewLoader-armeabi-v7a]:pid:1400 20387.599509 : 1127-ActivityManager : AP_Init:[]:[WebViewLoader-arm64-v8a]:pid:1401 20398.989970 : 1127-ActivityManager : AP_Init:[service]:[android.ext.services]:[{android.ext.services/android.ext.services.autofill.InlineSuggestionRenderServiceImpl}]:pid:1545 20516.452355 : 1127-ActivityManager : AP_Init:[added application]:[com.android.networkstack.process]:[com.android.networkstack.process]:pid:1451:(PersistAP) 20538.621586 : 1093-system_server : Keyguard bindService 20542.673586 : 1127-ActivityManager : AP_Init:[added application]:[com.android.se]:[com.android.se]:pid:1481:(PersistAP) 20543.482894 : 1093-system_server : Android:SysServerInit_END 20566.420432 : 1127-ActivityManager : AP_Init:[added application]:[com.hq.brightness]:[com.hq.brightness]:pid:1494:(PersistAP) 20585.782279 : 1127-ActivityManager : AP_Init:[added application]:[com.android.systemui]:[com.android.systemui]:pid:1505:(PersistAP) 20613.765894 : 1127-ActivityManager : AP_Init:[added application]:[com.hq.timesync.service]:[com.hq.timesync.service]:pid:1517:(PersistAP) 20635.150279 : 1127-ActivityManager : AP_Init:[top-activity]:[com.sgmw.launcher]:[{com.sgmw.launcher/com.sgmw.launcher.MainActivity}]:pid:1531 20666.003433 : 1127-ActivityManager : AP_Init:[service]:[android.ext.services]:[{android.ext.services/android.ext.services.autofill.InlineSuggestionRenderServiceImpl}]:pid:1545 20830.106587 : 1127-ActivityManager : AP_Init:[service]:[com.aispeech.lyra.daemon]:[{com.aispeech.lyra.daemon/com.aispeech.unit.smartapp.model.AccessibilityActionService}]:pid:1632 23117.411131 : 1115-android.display : AMS:ENABLE_SCREEN 23264.970593 : OFF----------------------------------------System Cold Boot Optimization – Optimization Measures
Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.
Optimize boot time from the startup sequence of each module
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Bootloader section — Optimization target: within 2 seconds
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Kernel section — Optimization target: within 1 second
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Android section — Optimization target: within 4 seconds
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Boot animation section — Optimization target: within 2 seconds
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Launcher section — Optimization target: within 1 second
Optimize boot time from the perspective of system resources
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Maximize resource utilization during boot; after boot, restore to normal resource usage (CPU, GPU, IO, etc.)
CPU: Depending on the platform, bring all online, raise the frequency to the maximum, remove power limits.
GPU: Boost.
IO: Tune read_ahead_kb and nr_requests according to the project’s actual situation.
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Maximize resource utilization for specific processes
Take the process shown in the figure as an example, giving it a higher I/O scheduling and process scheduling priority.
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Filesystem optimization
Conclusion
The process of optimizing system cold boot is actually a process of trade-offs, just as software inherently carries the wisdom of trading time for space and space for time.