Re: Preemption question (4xx related)

[Josh Boyer <jwboyer@linux.vnet.ibm.com>]

On Fri, Jul 03, 2009 at 08:41:00AM +1000, Benjamin Herrenschmidt wrote:
>On Thu, 2009-07-02 at 07:12 -0400, Josh Boyer wrote:
>> On Thu, Jul 02, 2009 at 05:33:12PM +1000, Benjamin Herrenschmidt wrote:
>> >On Wed, 2009-07-01 at 20:14 -0400, Josh Boyer wrote:
>> >
>> >> I've toyed with that idea myself.  I keep coming back to the fact that you need
>> >> a workload that would really leverage it, and I don't have one at the moment.
>> >
>> >To some extent that's true but just turning full preemption including
>> >kernel side with all the associated debug bits and lockdep should make a
>> >whole bunch of things show up even with ordinary workloads.
>> 
>> I can look at doing that for ppc44x_defconfig.  I'll be honest and say I don't
>> expect it to go well, particularly with lockdep :).
>> 
>> >For 440 tend to boot an ubuntu distro off NFS root with all X & DRI 3D
>> >etc... and then run compiz :-)
>> 
>> Yes.  Because that's a totally realistic workload for a 440.  I'm surprised you
>> don't have a p595 machine acting as your home router too!  ;)
>
>It doesn't need to be realistic. In fact, a "realistic" workload is the
>worst thing to test with because it won't exercise all the "uncommon"
>code path which are the ones likely to bite.
>
>So yesm it's not a "realistic" workload, but it's a good "torture"
>workload to find bugs.

It was a joke.  But yes, you make perfectly valid points :)

josh