svn commit: r222980 - in head/sys: amd64/conf i386/conf

Alexander Best arundel at freebsd.org
Sat Jul 2 19:05:34 UTC 2011


On Sat Jul  2 11, Ulrich Spörlein wrote:
> On Sat, 11.06.2011 at 13:55:15 -0700, Doug Barton wrote:
> > On 6/11/2011 1:02 PM, Warner Losh wrote:
> > >
> > > On Jun 11, 2011, at 12:17 PM, Doug Barton wrote:
> > >
> > >> On 6/11/2011 6:07 AM, Robert Watson wrote:
> > >>> To me, this seems like the wrong direction.  Over the last decade, we've
> > >>> been trying to move away from conditional compilation of features to
> > >>> having them be loadable as modules.
> > >>
> > >> FWIW, I agree. I'm wondering though, is there still a performance penalty for modules? My understanding in the past was that there is, although for most use cases it's in the statistical noise. Is that still true?
> > >
> > > At run time, I believe that's true.  At load time, lots of modules can take a few seconds longer.
> > 
> > I have 3 or 4 modules loaded via loader.conf at boot time. They take at 
> > least 2 seconds each. IMO loading everything via loader.conf would slow 
> > the boot so much as to be a non-starter.
> > 
> > OTOH, I could imagine an rc.d script that depends on mountcritlocal that 
> > could load a list of modules. Unless I'm missing something that would be 
> > several times faster.
> 
> I suspect this is your BIOS' fault. I load 22 modules via loader.conf
> and the loader takes 2, at most 3, seconds to load them all (next to the
> kernel). This is true for all machines that I own/owned.

actually i recenly switched from using kernel modules to one big kernel entity,
simply because i had the same problem. each module was taking ~ 3-5 seconds to
load. make that 10 modules and you have additional loading time of almost half
a minute. now that i'm using one big kernel entity i was able to reduce the
loading time to ~ 4 seconds plus an extra 3 seconds for nvidia.ko.

i could upload two videos demonstrating the huge differences between both
schemes on my computer, if somebody is interested in it.

cheers.
alex

> 
> As you can guess, I'm very much in favour of moving modules from GENERIC
> to loader.conf ...
> 
> Uli


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