UDS Developments

[Kaj Ailomaa]

On 05/08/2012 09:45 PM, Scott Lavender wrote:
> On Tue, May 8, 2012 at 11:02 AM, Ralf Mardorf<ralf.mardorf at alice-dsl.net>wrote:
>
>>
>> I've got no time to read the whole thread, since I need to repair my
>> mixer. However, for a full preempt non-rt kernel there is no patch
>> required. It only depends to the config of a vanilla kernel.
>>
>> Regarding to the CONFIG options in the previous post, there are some
>> CONFIG options missing, but those are already set for e.g. the
>> lowlatency kernel for Ubuntu Studio precise.
>>
>> Regards,
>> Ralf
>>
>>
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>>
>
>
> I apologize.  I realize my previous email was not as clear as I intended.
>
> Ralph, the patch I mentioned was for the delta against the official Ubuntu
> kernel.  For those who are not aware, Studio starts with the official
> Ubuntu kernel and changes a few compile flags.  These changes are applied
> in a patch.
>
> Also, I meant to say that it seems disproportionate that the -lowlatency
> kernel needs to be MANUALLY rebuilt for every kernel update given how close
> they are and how easy it appears it can be automated with config options.
>
>
>
>

I don't think this is true.

There are at least two separate things that differ between the 
ubuntu-precise kernel, and the ubuntu-precise-lowlatency kernel.

One is a patch to the code (which I assume is the two line patch that 
has been under discussion), which as I explained previously will not be 
needed anymore.
The other is the configuration used for the build. For the 
configuration, we only need to set a few configs differently from the 
standard ubuntu kernel (it's a long list), so that we get our 
-lowlatency flavor kernel.

And after adding the configs that Ralph mentioned to the ones that we 
already have specific for -lowlatency, as well as the configs that makes 
the current patch unnessecary, we get this list:

CONFIG_CMDLINE_BOOL=y
CONFIG_CMDLINE="threadirqs"
# CONFIG_RCU_BOOST is not set
# CONFIG_NTP_PPS is not set
# CONFIG_RCU_CPU_STALL_DETECTOR is not set
# CONFIG_RCU_CPU_STALL_VERBOSE is not set
# CONFIG_PREEMPT_TRACER is not set
CONFIG_TREE_PREEMPT_RCU=y
CONFIG_PREEMPT_RCU=y
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
CONFIG_PREEMPT=y
CONFIG_HZ_1000=y
CONFIG_HZ=1000
CONFIG_SLAB=y
# CONFIG_EXPERT is not set
# CONFIG_NO_HZ is not set
# CONFIG_DEBUG_KERNEL is not set

Using these configs on top of the default configs for the ubuntu-precise 
kernel we get our current -lowlatency.