Re: [PATCH 00/10] mm: PCP high auto-tuning

[Huang, Ying]

Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:

> On Thu, 21 Sep 2023 21:32:35 +0800 "Huang, Ying" <ying.huang@xxxxxxxxx> wrote:
>
>> >   : It's possible that PCP high auto-tuning doesn't work well for some
>> >   : workloads.  So, when PCP high is tuned by hand via the sysctl knob,
>> >   : the auto-tuning will be disabled.  The PCP high set by hand will be
>> >   : used instead.
>> >
>> >   Is it a bit hacky to disable autotuning when the user alters
>> >   pcp-high?  Would it be cleaner to have a separate on/off knob for
>> >   autotuning?
>> 
>> This was suggested by Mel Gormon,
>> 
>> https://lore.kernel.org/linux-mm/20230714140710.5xbesq6xguhcbyvi@xxxxxxxxxxxxxxxxxxx/
>> 
>> "
>> I'm not opposed to having an adaptive pcp->high in concept. I think it would
>> be best to disable adaptive tuning if percpu_pagelist_high_fraction is set
>> though. I expect that users of that tunable are rare and that if it *is*
>> used that there is a very good reason for it.
>> "
>> 
>> Do you think that this is reasonable?
>
> I suppose so, if it's documented!
>
> Documentation/admin-guide/sysctl/vm.rst describes
> percpu_pagelist_high_fraction.

Sure.  Will add document about auto-tuning behavior in the above
document.

--
Best Regards,
Huang, Ying