>
> On Sat, Sep 28, 2019, 20:13 Jason Kridner wrote:
>
>> I’m attending Sketching in Hardware <http://sketching-in-hardware.com/> this
>> weekend and there was a fair bit of discussion regarding how long it takes
>> to boot Linux and barriers it makes to understanding a system. My assertion
>> was that booting Linux on a computer, like PocketBeagle, doesn’t take very
>> long at all and that it generally only gets in the way when you want it.
>>
>> Here’s what I hacked up in about 10 minutes to show off how we can get a
>> whole lot of distribution code out-of-the-way.
>>
>> In /boot/uEnv.txt, I edited the cmdline:
>>
>> cmdline=coherent_pool=1M net.ifnames=0 rng_core.default_quality=100 quiet
>> *modules-load=g_serial*
>>
>> The point of this is that our boot script that configures the USB gadget
>> won’t be loaded anymore. This causes the Linux kernel to emulate a serial
>> port, providing a way to get to the Python REPL.
>>
>> In /etc/passwd, I edited the shell for the ‘debian’ user:
>>
>> debian:x:1000:1000:Demo User:/home/debian:*/usr/bin/python3*
>>
>> This makes python3 the default shell for the ‘debian’ user, so whenever a
>> user logs in as ‘debian’, they get a python3 REPL.
>>
>> In /lib/systemd/system/[email protected], I enabled a bypass for the
>> user login password request:
>>
>> ExecStart=-/sbin/agetty --keep-baud 115200,38400,9600 %I $TERM* -a
>> debian*
>>
>> This totally insecure, but on PocketBeagle without any augmentation, this
>> just gives access over the USB port. Seems pretty reasonable to me.
>>
>> I executed the following commands to reduce the applications running at
>> startup and enable the terminal on the virtual serial port:
>>
>> sudo systemctl set-default rescue.target
>> sudo ln -s /lib/systemd/system/[email protected]
>> /etc/systemd/system/default.target.wants/[email protected]
>>
>> When you do the above, a reboot will no longer bring up things like the
>> Cloud9 IDE, so be sure to run both commands before rebooting. Use ‘sudo
>> shutdown -r now’ to reboot.
>>
>> Seems like there’s still a fair amount of optimization that can be done,
>> but here’s the behavior I saw when pulling and re-inserting the USB cable
>> after making these changes:
>>
>> jkridner@tupper:~$ *journalctl -f*
>> Sep 28 13:55:52 tupper kernel: usb 1-4: USB disconnect, device number 26
>> Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on
>> /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:2.1
>> Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on
>> /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:2.0
>> Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on
>> /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4
>> Sep 28 13:56:08 tupper kernel: usb 1-4: new high-speed USB device number 27
>> using xhci_hcd
>> Sep 28 13:56:08 tupper kernel: usb 1-4: New USB device found,
>> idVendor=0525, idProduct=a4a7
>> Sep 28 13:56:08 tupper kernel: usb 1-4: New USB device strings: Mfr=1,
>> Product=2, SerialNumber=0
>> Sep 28 13:56:08 tupper kernel: usb 1-4: Product: Gadget Serial v2.4
>> Sep 28 13:56:08 tupper kernel: usb 1-4: Manufacturer: Linux
>> 4.14.108-ti-r113 with musb-hdrc
>> Sep 28 13:56:08 tupper kernel: cdc_acm 1-4:2.0: ttyACM0: USB ACM device
>>
>> So, without any other tweaking, it seems to still be taking about 16
>> seconds. I’m not very happy with this, so I’ll be hooking up a serial cable
>> and figuring out where the time goes soon.
>>
>> jkridner@tupper:~$ *tio /dev/ttyACM0*
>> [tio 14:02:10] tio v1.29
>> [tio 14:02:10] Press ctrl-t q to quit
>> [tio 14:02:10] Connected
>>
>> File "", line 0
>>
>> ^
>> SyntaxError: 'utf-8' codec can't decode byte 0xf0 in position 2: invalid
>> continuation byte
>> >>> quit()
>>
>> Debian GNU/Linux 9 beaglebone ttyGS0
>>
>> BeagleBoard.org Debian Image 2019-08-03
>>
>> Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian
>>
>> default username:password is [debian:temppwd]
>>
>> beaglebone login: debian (automatic login)
>>
>> Last login: Sun Aug 4 02:10:35 UTC 2019 on ttyGS0
>>
>> The programs included with the Debian GNU/Linux system are free software;
>> the exact distribution terms for each program are described in the
>> individual files in /usr/share/doc/*/copyright.
>>
>> Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
>> permitted by applicable law.
>> Python 3.5.3 (default, Sep 27 2018, 17:25:39)
>> [GCC 6.3.0 20170516] on linux
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> *import os*
>> >>> *os.system("bash")*
>> debian@beaglebone:~$
>>
>> I chose to use ‘tio’, but ‘screen’ and other serial utilities would work
>> fine.
>>
>> I don’t actually know that the cause of the stray characters is. Someone
>> can probably enlighten me.
>>
>> I’ll release this as a blog post once I figure out why the boot time is
>> this slow, but I thought this was interesting enough to post here. Enjoy.
>>
> A quick grabserial log:
[0.000001 0.000001]
[0.000084 0.000083] U-Boot SPL 2019.04-00002-gbb4af0f50f (Jul 08 2019 -
11:44:39 -0500)
[0.048198 0.048114] Trying to boot from MMC1
[0.128443 0.080245] Loading Environment from EXT4... ** File not found
/boot/uboot.env **
[0.176759 0.048316]
[0.176803 0.000044] ** Unable to read "/boot/uboot.env" from mmc0:1 **
[0.257320 0.080517]
[0.257422 0.000102]
[0.257473 0.000051] U-Boot 2019.04-00002-gbb4af0f50f (Jul 08 2019 - 11:44:39
-0500), Build: jenkins-github_Bootloader-Builder-128
[0.261285 0.003812]
[0.261331 0.000046] CPU : AM335X-GP rev 2.1
[0.262184 0.000853] I2C: ready
[0.305677 0.043493] DRAM: 512 MiB
[0.353349 0.047672] No match for driver 'omap_hsmmc'
[0.354567 0.001218] No match for driver 'omap_hsmmc'
[0.392303 0.037736] Some drivers were not found
[0.393526 0.001223] Reset Source: Global external warm reset has occurred.
[0.396006 0.002480] Reset Source: Power-on reset has occurred.
[0.398008 0.002002] RTC 32KCLK Source: Internal.
[0.399596 0.001588] MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
[0.401448 0.001852] Loading Environment from EXT4... ** File not found
/boot/uboot.env **
[0.500941 0.099493]
[0.500992 0.000051] ** Unable to read "/boot/uboot.env" from mmc0:1 **
[0.574400 0.073408] Model: BeagleBoard.org PocketBeagle
[0.575353 0.000953] <ethaddr> not set. Validating first E-fuse MAC
[0.576464 0.001111] Net: usb_ether
[0.576935 0.000471] Press SPACE to abort autoboot in 2 seconds
[2.559828 1.982893] board_name=[A335PBGL] ...
Only a 1/2s of waste up to here. The 2s delay is intentional. I'm tempted to
set the boot environment and BOOTDELAY to clear this one.
[2.656112 0.096284] switch to partitions #0, OK
[2.657331 0.001219] mmc0 is current device
[2.736225 0.078894] SD/MMC found on device 0
[2.762987 0.026762] gpio: pin 56 (gpio 56) value is 0
[2.764810 0.001823] gpio: pin 55 (gpio 55) value is 0
[2.766536 0.001726] gpio: pin 54 (gpio 54) value is 0
[2.768192 0.001656] gpio: pin 53 (gpio 53) value is 1
[2.770000 0.001808] starting USB...
[2.770900 0.000900] USB0: Port not available.
[3.755765 0.984865] gpio: pin 54 (gpio 54) value is 1
hmmm.... that's quite a delay. This also seems like a good candidate for
elimination with configuring the boot environment.
[3.771881 0.016116] Checking for: /boot/uEnv.txt ...
[3.877247 0.105366] switch to partitions #0, OK
[3.878375 0.001128] mmc0 is current device
[3.879302 0.000927] gpio: pin 56 (gpio 56) value is 0
[3.880383 0.001081] gpio: pin 55 (gpio 55) value is 0
[3.881447 0.001064] gpio: pin 54 (gpio 54) value is 0
[3.882650 0.001203] gpio: pin 53 (gpio 53) value is 1
[3.957024 0.074374] switch to partitions #0, OK
[3.958922 0.001898] mmc0 is current device
[4.036965 0.078043] gpio: pin 54 (gpio 54) value is 1
[4.117177 0.080212] Checking for: /uEnv.txt ...
[4.149090 0.031913] Checking for: /boot.scr ...
[4.165031 0.015941] Checking for: /boot/boot.scr ...
[4.180923 0.015892] Checking for: /boot/uEnv.txt ...
[4.213085 0.032162] gpio: pin 55 (gpio 55) value is 1
[4.245069 0.031984] 2340 bytes read in 34 ms (66.4 KiB/s)
[4.246042 0.000973] Loaded environment from /boot/uEnv.txt
[4.278298 0.032256] debug: [dtb=am335x-pocketbeagle.dtb] ...
[4.280809 0.002511] Using: dtb=am335x-pocketbeagle.dtb ...
[4.283421 0.002612] Checking if uname_r is set in /boot/uEnv.txt...
[4.286133 0.002712] gpio: pin 56 (gpio 56) value is 1
[4.288118 0.001985] Running uname_boot ...
[4.293022 0.004904] loading /boot/vmlinuz-4.14.108-ti-r113 ...
[4.949998 0.656976] 9929216 bytes read in 657 ms (14.4 MiB/s)
Pretty big kernel, but not too bad to spend 1/2s here. Almost 10M. A trimmed
kernel would still be about 2M. A possible place to optimize, but one with big
trade-offs.
[4.966652 0.016654] debug: [enable_uboot_overlays=] ...
[5.002822 0.036170] loading /boot/dtbs/4.14.108-ti-r113/am335x-pocketbeagle.dtb
...
[5.064918 0.062096] 124423 bytes read in 54 ms (2.2 MiB/s)
[5.066676 0.001758] uboot_overlays: add [enable_uboot_overlays=1] to
/boot/uEnv.txt to enable...
[5.080701 0.014025] loading /boot/initrd.img-4.14.108-ti-r113 ...
[5.455137 0.374436] 4696515 bytes read in 326 ms (13.7 MiB/s)
If we aren't really running from this initrd, why spend the time to load it?
[5.457428 0.002291] debug: [console=ttyO0,115200n8 root=/dev/mmcblk0p1 ro
rootfstype=ext4 rootwait coherent_pool=1M net.ifnames=0
rng_core.default_quality=100 quiet modules-load=g_serial] ...
[5.464145 0.006717] debug: [bootz 0x82000000 0x88080000:47a9c3 0x88000000] ...
[5.466492 0.002347] ## Flattened Device Tree blob at 88000000
[5.467819 0.001327] Booting using the fdt blob at 0x88000000
[5.469190 0.001371] Loading Ramdisk to 8fb85000, end 8ffff9c3 ... OK
[5.487277 0.018087] Loading Device Tree to 8fb63000, end 8fb84606 ... OK
[5.503357 0.016080]
[5.503431 0.000074] Starting kernel ...
[5.504097 0.000666]
[7.040070 1.535973] [ 0.001542] timer_probe: no matching timers found
1.5s to before the kernel starts printing messages? Is this mostly due to
decompression? Certainly something to pay attention to here.
[7.062996 0.022926] [ 0.936616] wkup_m3_ipc 44e11324.wkup_m3_ipc: could not
get rproc handle
[7.237535 0.174539] [ 1.137073] omap_voltage_late_init: Voltage driver
support not added
[7.260652 0.023117] [ 1.144372] PM: Cannot get wkup_m3_ipc handle
[7.307415 0.046763] [ 1.208281] PM: Cannot get wkup_m3_ipc handle
[7.769046 0.461631] [ 1.651529] musb-hdrc musb-hdrc.1: VBUS_ERROR in
a_wait_vrise (80, <SessEnd), retry #3, port1 0008010c
Hmmm.... would this go away if I had something connected?
[12.556108 4.787062] rootfs: recovering journal
Ugh. Now this is serious. Should I have the file system mounted read-only and
only have Python scripts switch it to writable as-needed? I cannot expect
people will perform consistent graceful shutdowns.
[12.636161 0.080053] rootfs: clean, 83681/230144 files, 589372/920576 blocks
[18.112197 5.476036] You are in rescue mode. After logging in, type "journalctl
-xb" Give root password for maintenance
Hmmm. What am I missing about what is going on here? Is this more file system
work or something else in the system. I probably need to overlay a systemd
report here...
[18.304912 0.192715] (or press Control-D to continue):
root@beaglebone:~# systemd-analyze
Startup finished in 7.153s (kernel) + 4.770s (userspace) = 11.924s
root@beaglebone:~# systemd-analyze blame
10.874s dev-mmcblk0p1.device
2.791s systemd-udev-trigger.service
2.124s keyboard-setup.service
1.175s systemd-journald.service
704ms systemd-modules-load.service
682ms systemd-tmpfiles-setup-dev.service
565ms sys-kernel-debug.mount
548ms systemd-random-seed.service
545ms systemd-timesyncd.service
414ms systemd-sysctl.service
382ms kmod-static-nodes.service
381ms systemd-udevd.service
323ms systemd-remount-fs.service
255ms dev-mqueue.mount
241ms sys-kernel-config.mount
238ms systemd-update-utmp.service
227ms sys-fs-fuse-connections.mount
223ms systemd-tmpfiles-setup.service
207ms systemd-journal-flush.service
174ms systemd-update-utmp-runlevel.service
OK then. Booting from microSD on an unclean filesystem is rough. Thoughts?
--
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