Re: [PATCH] Expose sysctls for enabling slab/file_cache interleaving

From: KOSAKI Motohiro
Date: Wed Nov 20 2013 - 00:50:03 EST


On Tue, Nov 19, 2013 at 4:49 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> Michal Hocko <mhocko@xxxxxxx> writes:
>>
>> Another option would be to use sysctl values for the top cpuset as a
>> default. But then why not just do it manually without sysctl?
>
> I want to provide an alternative to having to use cpusets to use this,
> that is actually usable for normal people.
>
> Also this is really a global setting in my mind.
>
>> If you create a cpuset and explicitly disable spreading then you would
>> be quite surprised that your process gets pages from all nodes, no?
>
> If I enable it globally using a sysctl I would be quite surprised
> if some cpuset can override it.
>
> That argument is equally valid :-)
>
> The user configured an inconsistent configuration, and the kernel
> has to make a decision somehow.
>
> In the end it is arbitary, but not having to check the cpuset
> here is a lot cheaper, so I prefer the "sysctl has priority"
> option.

sorry.
I agree with Michael. If there are large scope knob and small scope knob,
the small scope should have high priority. It is one of best practice of the
interface design.

However, I fully agree the basic concept of this patch. sysctl help a
lot of admins.
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