Re: [PATCH 2/2] mm/slub: disable merging after enabling debug in runtime

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

On 17.07.2015 18:09, Christoph Lameter wrote:
> On Fri, 17 Jul 2015, Konstantin Khlebnikov wrote:
>
>>> Hrm.... Bad. Maybe drop the checks for the debug options that can be
>>> configured when merging slabs? They do not influence the object layout
>>> per definition.
>>
>> I don't understand that. Debug options do changes in object layout.
>
> Only some debug options change the object layout and those are alrady
> forbidden for caches with objects.

Ah, ok. I've missed that any_slab_objects(). Never used enabling these 
features in runtime.

>
>> Since they add significant performance overhead and cannot be undone in runtime
>> it's unlikely that anyone who uses them don't care about merging after that.
>
> Those that do not affect the object layout can be undone.

Except __CMPXCHG_DOUBLE. But I guess we can use stop-machine for that.

>
>> Also I don't see how merging could affect debugging in positive way
>> (except debugging bugs in merging logic itself).
>
> The problem here is that debugging is switched on for slabs that are
> already merged right?
>

Right. And looks like problem only in conflicting sysfs names.

-- 
Konstantin

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