Am 08.01.25 um 19:33 schrieb Bird, Tim:
-----Original Message----- From: Shankari <beingcap11@xxxxxxxxx> Hi I wanted to provide an update on my recent contributions to the boot-time reduction project. I have recently started contributing and am working with the beagleplay. I have been analyzing the boot time of the init process. Below is the output from the system log: debian@BeaglePlay:~$ dmesg | grep "init process" [ 1.480490] Run /init as init process Moving forward, I plan to explore ways to modify the command line and further investigate the data used for SIG analysis. This will help me gain a deeper understanding of the boot process and its performance characteristics. Please let me know if you have any suggestions or areas where I could focus my efforts.Hi Shankari, It sounds like you are off to a good start. I have something that needs to be done, that I think you can help with, and that matches where I believe you are in your status with being able to evaluate the kernel. In general, there's a lot of information on the elinux wiki which is stale, which needs to be updated or archived, or maybe even just removed. This section of the Boot Time page has a lot of material in this category: https://elinux.org/Boot_Time#kernel_speedups Can you validate the information on these 2 pages: * https://elinux.org/Disable_Console * https://elinux.org/Preset_LPJ This would consist of reading through the material, and testing the described techniques on your machine. This will involve booting the machine 2 ways, with a particular kernel command line option and without it, and then reporting back the final boot time for both. You can use the timestamp for the "init process" string as your final boot time, for the purposes of this exercise. Helping me to update the elinux wiki material on boot time would be an immense help, and is one of my main goals for the boot time SIG in 2025. Don't hesitate to ask questions if you have any. BTW - you can just report your findings to me and linux-embedded list, but alternatively (and even better) would be if you could also update the wiki pages themselves with your information based on recent kernels and hardware. To do this, you will need an elinux wiki account, which you can make online on elinux wiki.org by going to this page: https://elinux.org/Special:CreateAccount Anyone else reading this who wants to also participate in this project to update the elinux wiki boot time information, please contact me. Thanks. -- Tim
Hi Tim, all,first time I'm posting here so hopefully everything is fine w/ my mail format / attachment and so on ... If not, please give me some feedback and guidance.
To the "disable console" topic: I have some numbers in place for an RPI Zero W, find dmesg dumps and systemd-analyze plots attached.
Environment: - RPi Zero W, kernel 5.15.24, systemd 247.3, customized debian - onboard UART used Cases:- #1 quiet: cmdline w/ quiet, no kernel or userspace output up to the serial login console
- #2 normal: cmdline w/o quiet, serial console @115200 baud - #3 normal_baud9600: cmdline w/o quiet, serial console @9600 baud Main outcomes: - kernel timestamps "Run /sbin/init as init process" #1: "1.714458", #2: "3.011701", #3: "16.108101" Interpretation: * enabled serial console has significant impact in kernel boot time * reducing baud to 9600 induced some side effect, not sure what it is ... - systemd startup * systemd drops 2 log lines per started unit to the console* seems serial output is not implemented asynchronously (see steps of units in sd plot, ~10ms per unit w/ baud 115200, ~80ms per unit w/ baud9600
Side notes: * I remember similar behavior w/ imx.6 SoCs* Maybe this issues is not seen on other SoCs (maybe w/ another hw implementation of the UART)
* Maybe this issues is only seen in single core machines (I can double check w/ a PI3 or orange pi zero once)
Hope this helps. Regards, Marko
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