OpenBMC kernel and CONFIG_PREEMPT

[William Kennington]

I just looked again, AFAICT it was never enabled on aspeed or npcm7xx, just
the new 8xx part. Hopefully someone else with aspeed chips will confirm
from their actual `.config`

On Fri, Apr 7, 2023 at 1:05 PM William Kennington <wak at google.com> wrote:

> It's interesting because I think it has a bigger impact on the 8xx chip
> than the 7xx chip. AFAIK I was indirectly comparing this and it seems like
> it didn't make a huge difference for us on our older BMCs. We have it
> disabled on our 5.15 configs, but used it in 5.10. I don't think we noticed
> a meaningful difference when porting forward. Probably you need a certain
> amount of startup services trying to steal time from each other.
>
> On Fri, Apr 7, 2023 at 12:10 PM Patrick Williams <patrick at stwcx.xyz>
> wrote:
>
>> Joel,
>>
>> Would you mind looking at this commit[1]?  Nuvoton seems to have a lot
>> of data that suggests that disabling CONFIG_PREEMPT leads to
>> significantly better performance.  The boot time is almost 50% faster.
>>
>> I'm surprised that:
>>
>>     1. CONFIG_PREEMPT really results in that worse of performance.
>>     2. The Nuvoton chip is special from any other ARM variant in this
>>        regard.
>>
>> Should we disable this across the board on all our platforms?
>>
>> 1.
>> https://github.com/openbmc/openbmc/commit/52ec37dd0b8776ce7f43e65e0be578c3606340b7
>> --
>> Patrick Williams
>>
>
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