[systemd-devel] device units rely on udev rules?

[microcai]

于 2011年05月10日 03:51, Koen Kooi 写道:
> 
> Op 9 mei 2011, om 21:43 heeft Lennart Poettering het volgende geschreven:
> 
>> On Mon, 09.05.11 11:53, Scott James Remnant (scott at netsplit.com) wrote:
>>
>>> Another question I wasn't able to find an answer to in the documentation
>>> I've read so far.
>>>
>>> The use of device units seems to very much rely on udevd running on the
>>> system, and not only that, udev rules having been parsed for the device and
>>> a systemd tag "set" in the udevdb. udev obviously starts after systemd, and
>>> systemd starts after the kernel.
>>
>> Correct.
>>
>>> This means there are a large number of devices already known to the kernel
>>> at the point that systemd starts, especially if you build the drivers into
>>> the kernel for those devices. It's possible to get going straight away with
>>> those devices. But relying on udevd tagging them means you end up waiting
>>> around for udevd to start, and worse! since udevd doesn't apply rules to
>>> existing devices on startup, you have to wait around for "udevadm trigger"
>>> to be run.
>>
>> That's actually dead fast
> 
> It's still in the 10 second range on a 600MHz cortex-a8 machine booting from an SD card. I need to dig out my 400MHz arm920t to see how long it takes there. So having udev-less operation in systemd would be nice, even if it's only used on 'embedded'

I had an ARM9  with Gentoo + systemd installed.

Systemd itself boot system in about 20s. But it tooks 10s+ to mount the
yaffs2 root fs. So, 30s+ to boot.

Hope this data will be useful to you.


> 
> regards,
> 
> Koen
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> systemd-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/systemd-devel


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