[systemd-devel] Antw: Re: device enumeration by systemd user instances

[Ulrich Windl]

>>> Greg KH <gregkh at linuxfoundation.org> schrieb am 25.07.2019 um 17:45 in
Nachricht <20190725154555.GA6487 at kroah.com>:
> On Thu, Jul 25, 2019 at 05:29:33PM +0200, Pawel Szewczyk wrote:
>> On 7/17/19 23:14, Greg KH wrote:
>> > 
>> > 100ms seems like a really long time, what exactly is it doing during
>> > that time?  Is the kernel spending too much time regenerating the
>> > uevents?
>> > 
>> > How many devices are you talking about?  Any chance to see what really
>> > is happening here by running perf to see where the hot-spots are?
>> 
>> There are ~80 devices being enumerated and 1ms per device still seem a 
>> little too long. Note, that we are running this on arm architecture.

I wonder: Doesn't that depend on the individual devices? I can remember that "Scanning the SCSI bus" in HP-UX had always been a matter of minutes...

>> 
>> Maybe using perf or other tools to find out what exactly is taking this 
>> time is a good idea (never used perf to be honest). For now just by 
>> adding some verbose logs it seems that processing of each device 
>> actually takes around 1ms.
> 
> Run perf and see what is going on, that seems like way too long per
> device.
> 
> thanks,
> 
> greg k-h
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