Re: [RFC] SL[AUO]B common code 5/9] slabs: Common definition for boot state of the slab allocators

[Glauber Costa <glommer@parallels.com>]

On 05/16/2012 06:31 PM, Christoph Lameter wrote:
>> There are a couple of places where that test seems to be okay (I remember 1 in
>> >  the slub), but at least for the "FULL" test here, we should be testing>=
>> >  FULL.
>> >
>> >  Also, I don't like the name FULL too much, since I do intend to add a new one
>> >  soon (MEMCG, as you can see in my series)
> Ok. Why would memcg need an additional state?

Please refer to my patchset for the full story.
I add state both to the slab and to the slub for that.

But in summary, it is not unlike the "SYSFS" state: we depend on 
something else outside of the slab domain to be ready before we can proceed.

Specifically, we need to register each cache with an index. And for 
that, we use idr/ida. When it is ready, we run code to register indexes 
for all caches that are already available. After that, we just grab an 
index right away - much like sysfs state for aliases.

>> >  Since we are using slab-specific states like PARTIAL_L3 here, maybe we can use
>> >  slub's like SYSFS here with no problem.
> Sure. I thought there would only be special states before UP.
>
>> >  If we stick to>= and<= whenever needed, that should reflect a lot better
>> >  what the algorithm is really doing
> How so?

In the sense that we very rarely want to do some action *at a specific 
moment*. Most of the time we want to separate the world into before and 
after a state. We test == instead of <= and >=, and it happens to work 
because of the specific order of things, which are subject to change in 
a rework or another...


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