linux-kernel - Reduce init time of `lp_init()` and `ppdev

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Date:   Thu, 29 Mar 2018 17:57:20 +0200
From:   Paul Menzel <pmenzel+linux-char@...gen.mpg.de>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Reduce init time of `lp_init()` and `ppdev_init()`

Dear Linux folks,


I am trying to reduce the start-up time of the Linux kernel on an old 
Lenovo X60. Looking through the time stamps of Linux 4.16-rc7+, the 
modules `lp` and `ppdev` both take more than ten milliseconds to 
initialize according to `initcall_debug`.

```
[    8.337692] calling  parport_default_proc_register+0x0/0x1000 
[parport] @ 245
[    8.337735] initcall parport_default_proc_register+0x0/0x1000 
[parport] returned 0 after 30 usecs
[    8.359066] calling  lp_init_module+0x0/0x1000 [lp] @ 245
[    8.381317] lp: driver loaded but no devices found
[    8.385310] initcall lp_init_module+0x0/0x1000 [lp] returned 0 after 
25613 usecs
[    8.401727] calling  ppdev_init+0x0/0x1000 [ppdev] @ 245
[    8.411427] ppdev: user-space parallel port driver
[    8.415390] initcall ppdev_init+0x0/0x1000 [ppdev] returned 0 after 
13329 usecs
[    8.434018] calling  parport_pc_init+0x0/0xeed [parport_pc] @ 245
[    8.435657] initcall parport_pc_init+0x0/0xeed [parport_pc] returned 
0 after 1589 usecs
[    9.343691] EXT4-fs (dm-0): re-mounted. Opts: errors=remount-ro,discard
[    9.742084] systemd-journald[271]: Received request to flush runtime 
journal from PID 1
[   10.049050] calling  acpi_cpufreq_init+0x0/0x1000 [acpi_cpufreq] @ 297
[   10.049668] initcall acpi_cpufreq_init+0x0/0x1000 [acpi_cpufreq] 
returned 0 after 581 usecs
```

Furthermore, looking at the messages, it looks like it’s in the 
“hotpath”. If that is true, is there a way to load that in parallel of 
the other Linux kernel stuff?

Hints to get more insight are much appreciated.


Kind regards,

Paul


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