Re: Good news for threading!

[Alan Jenkins <alan-jenkins@tuffmail.co.uk>]

Kay Sievers wrote:
> On Mon, May 25, 2009 at 22:28, Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
>   
>> Kay Sievers wrote:
>>     
>
>   
>>> Do you have numbers for the difference of threaded vs. non-threaded, for:
>>>  time (udevadm trigger; udevadm settle)
>>> when no rules are active?
>>>       
>
>   
>> Interesting question.  I stop HAL first, it tends to slow my tests down and
>> doesn't represent normal bootup.
>>     
>
> Yeah, it's the RUN+="socket: ..." handling, which can block the event
> process, if something listens, but does not read fast enough. With the
> new netlink events from udev to listeners (no RUN+="socket: ..."
> needed), the sending is de-coupled from the listeners state and will
> not slow-down udev. Hopefully HAL will go away soon, we are pretty
> close already.
>   

From my POV it's more that if I don't kill HAL, I think it appears
higher than udev in the profile.  So udev will have to compete for CPU
time, and I can't simply measure the elapsed time.

>> Test machine is eeepc 701; trigger -n shows 382 devices.
>>
>> no threading:    ~0.5s
>> threading:   ~0.25s
>>     
>
> Oh, nice numbers. In a real setup, can we expect more than 0.25s to
> win with a threaded udevd?

I don't know yet.  I need to re-implement the madvise hack so it doesn't
segfault on a booting system.

I'm pretty sure I know what I did wrong.  But right now I'm working on
submitting everything that's ready.

> What can we expect from the udev-exec
> thing? Will it be a bit slower, because it has a bit more work to do?
>   

I ditched the udev-exec daemon on Scotts suggestion.

Regards
Alan