Hi,
On 8/22/19 11:36 AM, Laura Abbott wrote:
On 8/22/19 8:58 AM, Prarit Bhargava wrote:
> On 8/19/19 9:15 AM, Laura Abbott wrote:
>> On 8/16/19 2:57 PM, Paul Bolle wrote:
>>> Florian Weimer schreef op vr 16-08-2019 om 14:04 [+0200]:
>>>> RHEL has a larger NR_CPU value, though. For example, it's 8192 on
>>>> x86-64, while Fedora 31 has 1024.
>>>
>>> On the Fedora x86-64 debug builds it's 8192 again. Why's that?
>>>
>>>
>>> Paul Bolle
>>>
>>
>> That's the option for max cpus. We don't want to turn it on in all
>> Fedora builds since it would use up more resources we probably don't
>> actually need. Turning on for debugging in Fedora is okay though.
>> RHEL is focused on larger footprints and makes the trade off to
>> have it enabled all the time.
>>
>
> I think I measured the impact of 8192 vs 512 (or 256?) a long time ago
> and we
> are talking about _k_ of memory. We should stick with what upstream
> has at
> 8192. It's easier to debug when we have the same value as the default
> IMO.
>
> Having said that, it has been a long time since I had to debug a
> NR_CPUS/nr_cpus
> issue in the kernel. We're just not seeing bugs around the value
> anymore.
>
I was going to ask about the actual impact of a larger number of CPUs.
If it's
actually only k of memory it's probably better to just set MAXCPUS all
the time.
Even the lowest end machines probably see more change when frameworks
change.
And yes, I also think that we've come a long way so NR_CPUS is less of
an important
option to optimize these days. I think I'll just submit another patch to
just do
the max cpus.
Forgive me if you have already posted (didn't see it yet).
Its probably a good idea to bump the aarch64 config at the same time.
Some aarch64 "desktop" machines is already at the 256 core limit
currently in use.
Thanks,
Laura
> P.
>
>> Thanks,
>> Laura
>>
>
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