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List:       linux1394-devel
Subject:    Re: fw_ohci_init takes 100 ms on Lenovo X60t during boot
From:       Clemens Ladisch <clemens () ladisch ! de>
Date:       2017-08-16 13:03:46
Message-ID: eb8d267c-2ab8-0ffa-5603-73e56f1c256a () ladisch ! de
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Paul Menzel wrote:
> The major time is spent with 32 ms in `__alloc_workqueue_key`,

Conflicts with other memory-allocating code running in parallel.
There's nothing we can do about this.

> and with 71 ms in `__pci_register_driver`.
>>         → pci_probe [firewire_ohci] (70.509 ms @ 3.481572)

Why can't this tool trace into this function?

Anyway, I guess that there is the same problem, i.e., some memory
allocations run into a global lock.

> Do you see away to speed this up?

There is a 50 ms sleep in ohci_enable() when waiting for LPS.  This
value is historical, and originally was used to wait once without
checking, so it should be possible to poll more often.

> As I don't use Firewire during boot, is there some way to autoload
> that functionality after boot, when a "cable" is plugged in?

The driver needs to initialize the hardware (and allocate memory for DMA)
to be able to detect that a cable has been plugged in.


Regards,
Clemens

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