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

[Aneesh Kumar K.V]

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?

-aneesh