Christophe Leroy's on April 3, 2019 4:31 am:
>
>
> 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.ku...@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
>>
>>
>> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 2 +-
>> arch/powerpc/include/asm/book3s/64/mmu.h | 48 +++++++++++--------
>> arch/powerpc/include/asm/book3s/64/slice.h | 6 +--
>> arch/powerpc/kernel/paca.c | 9 ++--
>> arch/powerpc/kernel/setup-common.c | 7 ++-
>> arch/powerpc/mm/hash_utils_64.c | 10 ++--
>> arch/powerpc/mm/mmu_context_book3s64.c | 16 ++++++-
>> arch/powerpc/mm/slb.c | 2 +-
>> arch/powerpc/mm/slice.c | 48 +++++++++----------
>> arch/powerpc/mm/subpage-prot.c | 8 ++--
>> 10 files changed, 91 insertions(+), 65 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> index a28a28079edb..d801be977623 100644
>> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> @@ -657,7 +657,7 @@ extern void slb_set_size(u16 size);
>>
>> /* 4 bits per slice and we have one slice per 1TB */
>> #define SLICE_ARRAY_SIZE (H_PGTABLE_RANGE >> 41)
>> -#define TASK_SLICE_ARRAY_SZ(x) ((x)->context.slb_addr_limit >> 41)
>> +#define TASK_SLICE_ARRAY_SZ(x)
>> ((x)->context.hash_context->slb_addr_limit >> 41)
>>
>> #ifndef __ASSEMBLY__
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h
>> b/arch/powerpc/include/asm/book3s/64/mmu.h
>> index a809bdd77322..07e76e304a3b 100644
>> --- a/arch/powerpc/include/asm/book3s/64/mmu.h
>> +++ b/arch/powerpc/include/asm/book3s/64/mmu.h
>> @@ -114,6 +114,33 @@ struct slice_mask {
>> DECLARE_BITMAP(high_slices, SLICE_NUM_HIGH);
>> };
>>
>> +struct hash_mm_context {
>> +
>> + u16 user_psize; /* page size index */
>
> Could we keep that in mm_context_t ?
Why do you want it there?
>> @@ -155,15 +155,15 @@ static struct slice_mask *slice_mask_for_size(struct
>> mm_struct *mm, int psize)
>> {
>> #ifdef CONFIG_PPC_64K_PAGES
>> if (psize == MMU_PAGE_64K)
>> - return &mm->context.mask_64k;
>> + return &mm->context.hash_context->mask_64k;
>
> You should take the two patches below, that would help:
> https://patchwork.ozlabs.org/patch/1059056/
> https://patchwork.ozlabs.org/patch/1059058/
Above patches seem good I think. What I think Aneesh should have is
is a macro or inline that gives a pointer to the hash_mm_context from
an mm_context pointer.
Architectures which always want it should just put the hash struct
in their mm_context struct and that avoids the pointer overhead
completely.
Thanks,
Nick
