Re: [PATCH] ALSA: hda: Request driver probe from an async task

[Paul Menzel <pmenzel+alsa-devel@molgen.mpg.de>]

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Dear Takashi,


On 04/24/18 14:15, Takashi Iwai wrote:
> On Tue, 24 Apr 2018 13:59:58 +0200,
> Paul Menzel wrote:

>> On 04/23/18 14:33, Takashi Iwai wrote:
>>> On Mon, 23 Apr 2018 14:30:36 +0200, Paul Menzel wrote:
>>
>>>> On 04/23/18 14:21, Takashi Iwai wrote:
>>>>> On Mon, 23 Apr 2018 14:05:52 +0200, Paul Menzel wrote:
>>>>>>
>>>>>> From: Paul Menzel <pmenzel@molgen.mpg.de>
>>>>>> Date: Sat, 24 Mar 2018 09:28:43 +0100
>>>>>>
>>>>>> On an ASRock E350M1, with Linux 4.17-rc1 according to `initcall_debug`
>>>>>> calling `azx_driver_init` takes sometimes more than a few milliseconds,
>>>>>> and up to 200 ms.
>>>>>>
>>>>>> ```
>>>>>> [    2.892598] calling  azx_driver_init+0x0/0xfe4 [snd_hda_intel] @ 218
>>>>>> [    2.943002] initcall azx_driver_init+0x0/0xfe4 [snd_hda_intel]
>>>>>> returned 0 after 49195 usecs
>>>>>> ```
>>>>>>
>>>>>> Trying to execute the Linux kernel in less than 500 ms, this is quite a
>>>>>> hold-up, and therefore request the probe from an async task.
>>>>>>
>>>>>> With this change, the test shows, that the function returns earlier.
>>>>>>
>>>>>> ```
>>>>>> [    3.254800] calling  azx_driver_init+0x0/0xfe4 [snd_hda_intel] @ 227
>>>>>> [    3.254887] initcall azx_driver_init+0x0/0xfe4 [snd_hda_intel]
>>>>>> returned 0 after 66 usecs
>>>>>> ```
>>>>>>
>>>>>> The same behavior is visible on a Dell OptiPlex 7010. The longer times
>>>>>> seem to happen, when the module *e1000e* is probed during the same time.
>>>>>>
>>>>>> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
>>>>>
>>>>> What actually took so long?  Could you analyze further instead of
>>>>> blindly putting the flag?
>>>>
>>>> Well, I am not sure. Could you please give me hints, how to debug this
>>>> further? Is there some debug flag?
>>>
>>> Usually perf would help, but even a simple printk() should suffice to
>>> see what's going on there :)
>>
>> Please find the messages for a 23 ms run below, and the debug patch
>> attached.
>>
>>> [    2.996238] calling  azx_driver_init+0x0/0xfe4 [snd_hda_intel] @ 214
>>> [    3.009838] calling  rtl8169_pci_driver_init+0x0/0x1000 [r8169] @ 217
>>> [    3.009904] r8169 Gigabit Ethernet driver 2.3LK-NAPI loaded
>>> [    3.010721] random: get_random_bytes called from ipv6_regen_rndid+0x2c/0x100 with crng_init=1
>>> [    3.011283] r8169 0000:03:00.0 eth0: RTL8168e/8111e at 0x(ptrval), bc:5f:f4:c8:d3:98, XID 0c200000 IRQ 26
>>> [    3.011289] r8169 0000:03:00.0 eth0: jumbo features [frames: 9200 bytes, tx checksumming: ko]
>>> [    3.013876] initcall rtl8169_pci_driver_init+0x0/0x1000 [r8169] returned 0 after 3917 usecs
>>> [    3.031754] calling  pcspkr_platform_driver_init+0x0/0x1000 [pcspkr] @ 221
>>> [    3.031904] input: PC Speaker as /devices/platform/pcspkr/input/input4
>>> [    3.032288] initcall pcspkr_platform_driver_init+0x0/0x1000 [pcspkr] returned 0 after 508 usecs
>>> [    3.034795] calling  psmouse_init+0x0/0x7c [psmouse] @ 220
>>> [    3.034903] initcall psmouse_init+0x0/0x7c [psmouse] returned 0 after 87 usecs
>>> [    3.043051] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.043154] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.043187] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.043198] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.043229] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.043265] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.043429] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.043479] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.043749] random: get_random_bytes called from key_alloc+0x1fc/0x5e0 with crng_init=1
>>> [    3.043973] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.045483] random: get_random_u32 called from arch_rnd.part.2+0x18/0x40 with crng_init=1
>>> [    3.045501] random: get_random_u32 called from load_elf_binary+0x76a/0x1d20 with crng_init=1
>>> [    3.045507] random: get_random_u32 called from arch_align_stack+0x45/0x70 with crng_init=1
>>> [    3.045528] random: get_random_u32 called from arch_rnd.part.2+0x18/0x40 with crng_init=1
>>> [    3.045558] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.045771] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.046127] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.046197] calling  pcsp_init+0x0/0x1000 [snd_pcsp] @ 221
>>> [    3.046206] Error: Driver 'pcspkr' is already registered, aborting...
>>> [    3.046337] initcall pcsp_init+0x0/0x1000 [snd_pcsp] returned -16 after 128 usecs
>>> [    3.046348] random: get_random_u32 called from arch_align_stack+0x45/0x70 with crng_init=1
>>> [    3.046363] random: get_random_bytes called from load_elf_binary+0xaf8/0x1d20 with crng_init=1
>>> [    3.046383] random: get_random_u32 called from randomize_page+0x42/0x57 with crng_init=1
>>> [    3.047312] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.048151] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.048638] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.054325] random: get_random_u32 called from copy_process.part.33+0x186/0x2100 with crng_init=1
>>> [    3.054371] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.067344] usb usb3: New USB device found, idVendor=1d6b, idProduct=0001, bcdDevice= 4.17
>>> [    3.067350] usb usb3: New USB device strings: Mfr=3, Product=2, SerialNumber=1
>>> [    3.067353] usb usb3: Product: OHCI PCI host controller
>>> [    3.067356] usb usb3: Manufacturer: Linux 4.17.0-rc2+ ohci_hcd
>>> [    3.067359] usb usb3: SerialNumber: 0000:00:12.0
>>> [    3.067850] random: get_random_u32 called from cache_random_seq_create+0xa3/0x1f0 with crng_init=1
>>> [    3.067864] hub 3-0:1.0: USB hub found
>>> [    3.067960] hub 3-0:1.0: 5 ports detected
>>> [    3.068141] random: get_random_u32 called from cache_alloc_refill+0x5bb/0x13d0 with crng_init=1
>>> [    3.068618] 1
>>> [    3.068644] 2
>>> [    3.068953] 3
>>> [    3.068954] 4
>>> [    3.068955] 5
>>> [    3.068959] 6
>>> [    3.068960] 7
>>> [    3.068966] 8
>>> [    3.068967] 9
>>> [    3.069204] 1
>>> [    3.069217] 2
>>> [    3.069565] 3
>>> [    3.069566] 4
>>> [    3.069567] 5
>>> [    3.069568] 6
>>> [    3.069569] 7
>>> [    3.069581] 8
>>> [    3.069583] 9
>>> [    3.069774] random: get_random_u32 called from copy_process.part.33+0x186/0x2100 with crng_init=1
>>> [    3.069924] initcall azx_driver_init+0x0/0xfe4 [snd_hda_intel] returned 0 after 23153 usecs
>>
>> Unfortunately, it looks like the time stamps of the Linux kernel and
>> the initcall_debug time do not match. From the Linux time stamps it
>> should be 73 ms.
> 
> Indeed.  But even from this result, you can have a rough idea.
> As you can see, the most of time was spent before "1" point, which is
> the very beginning of azx_probe().  That is, the slowness is not in
> HD-audio driver probe itself.  Rather it's likely because of parallel
> probing with other multiple devices.

I agree. But that also makes it clear, that the probe can be done in 
async task, doesn’t it?


Kind regards,

Paul


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