[RFC PATCH] powerpc/mm: Reduce memory usage for mm_context_t for radix

[Christophe Leroy]

Le 02/04/2019 à 17:42, Aneesh Kumar K.V a écrit :
> On 4/2/19 9:06 PM, Christophe Leroy wrote:
>>
>>
>> Le 02/04/2019 à 16:34, Aneesh Kumar K.V a écrit :
>>> Currently, our mm_context_t on book3s64 include all hash specific
>>> context details like slice mask, subpage protection details. We
>>> can skip allocating those on radix. This will help us to save
>>> 8K per mm_context with radix translation.
>>>
>>> With the patch applied we have
>>>
>>> sizeof(mm_context_t)  = 136
>>> sizeof(struct hash_mm_context)  = 8288
>>>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>>> ---
>>> NOTE:
>>>
>>> If we want to do this, I am still trying to figure out how best we 
>>> can do this
>>> without all the #ifdef and other overhead for 8xx book3e
>>
>> Did you have a look at my series 
>> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=98170 ?
>>
>> It tries to reduce as much as feasible the #ifdefs and stuff.
>>
>>
> 
> Not yet. But a cursory look tell me introducing hash_mm_context 
> complicates this further unless I introduce something similar for nohash 
> 32? Are you ok with that?

Have a look at my review in the other mail, I think we can limit the 
changes and avoid introducing the hash_mm_context for 8xx.

Otherwise, we should call it something else, for instance 
extended_mm_context, but that looks unnecessary from my point of view.

Christophe