Re: [GIT] Experimental threaded udev

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

Kay Sievers wrote:
> On Thu, May 28, 2009 at 16:35, Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
>   
>> Now available for your delight and/or horror.
>>
>> <http://github.com/sourcejedi/udev/commits/threading-v0.3>
>>
>> For now, I'm still treating this as a patch series.  That is, I may
>> publish future versions with a rewritten history.  I'll preserve the old
>> branches though.
>>
>> It turns out the MADV_DONTFORK hack I was so proud of is
>> implementation-dependant, i.e. a dirty hack.  However, I'm confident
>> that glibc can and should be modified to do it for all programs.  And it
>> is so worth it.  On my test machine, threading alone goes from 2s
>> boot-time coldplug to 1.3-ish.  MADV_DONTFORK takes it down to 0.7-ish.
>> The hack is contained in the last patch, "when forking a program, only
>> copy the stack of the _current_ thread".
>>     
>
> Is that a single or dual CPU box?
>   

Single CPU - its my Celeron 630Mhz netbook.

> With the threaded version, it's 0.18 (1.51 -> 1.33) seconds faster
> here for a full coldplug run on a:
> Intel(R) Core(TM)2 Duo CPU U9400  @ 1.40GHz.
>
> It might be that the threaded version will only behave that much
> better on a single CPU machine?
>
> Thanks,
> Kay
>   

I'll have a look on my Core2Duo desktop.  My netbook core is much slower
than a C2D desktop, but it does require explanation.

There are a couple of global locks.  The selinux context is per-process,
so that's locked.  If you don't have full close-on-exec support, it has
to fallback to locking.  I haven't tested the full close-on-exec support
yet.

My memory says my desktop machine steams through coldplug in a fraction
of a second, but I've not measured it recently.

Thanks
Alan