> Currently we copy the whole mm_context_t to the paca but only access a > few bits of it. This is wasteful of space paca and also takes quite > some time in the hot path of context switching. > > This patch pulls in only the required bits from the mm_context_t to > the paca and on context switch, copies only those. > > Benchmarking this (On top of Anton's recent MSR context switching > changes [1]) using processes and yield shows an improvement of almost > 3% on POWER8: > > http://ozlabs.org/~anton/junkcode/context_switch2.c > ./context_switch2 --test=yield --process 0 0
Now the context switch series is in, I tested this against powerpc-next and still see a ~3% improvement. Anton > 1. > https://lists.ozlabs.org/pipermail/linuxppc-dev/2015-October/135700.html > > Signed-off-by: Michael Neuling <mi...@neuling.org> > --- > arch/powerpc/include/asm/paca.h | 17 +++++++++++++++-- > arch/powerpc/kernel/asm-offsets.c | 8 ++++---- > arch/powerpc/mm/hash_utils_64.c | 4 ++-- > 3 files changed, 21 insertions(+), 8 deletions(-) > > diff --git a/arch/powerpc/include/asm/paca.h > b/arch/powerpc/include/asm/paca.h index 1cc6e08..1c0d9f4 100644 > --- a/arch/powerpc/include/asm/paca.h > +++ b/arch/powerpc/include/asm/paca.h > @@ -132,7 +132,13 @@ struct paca_struct { > #endif /* CONFIG_PPC_BOOK3E */ > > #ifdef CONFIG_PPC_BOOK3S > - mm_context_t context; > + mm_context_id_t context_id; > +#ifdef CONFIG_PPC_MM_SLICES > + u64 context_low_slices_psize; > + unsigned char context_high_slices_psize[SLICE_ARRAY_SIZE]; > +#else > + u16 context_sllp; > +#endif > #endif > > /* > @@ -199,7 +205,14 @@ struct paca_struct { > #ifdef CONFIG_PPC_BOOK3S > static inline void copy_mm_to_paca(mm_context_t *context) > { > - get_paca()->context = *context; > + get_paca()->context_id = context->id; > +#ifdef CONFIG_PPC_MM_SLICES > + get_paca()->context_low_slices_psize = > context->low_slices_psize; > + memcpy(&get_paca()->context_high_slices_psize, > + &context->high_slices_psize, SLICE_ARRAY_SIZE); > +#else > + get_paca()->context_sllp = context->sllp; > +#endif > } > #else > static inline void copy_mm_to_paca(mm_context_t *context){} > diff --git a/arch/powerpc/kernel/asm-offsets.c > b/arch/powerpc/kernel/asm-offsets.c index 9db7be2..d5903a9 100644 > --- a/arch/powerpc/kernel/asm-offsets.c > +++ b/arch/powerpc/kernel/asm-offsets.c > @@ -186,12 +186,12 @@ int main(void) > DEFINE(PACASOFTIRQEN, offsetof(struct paca_struct, > soft_enabled)); DEFINE(PACAIRQHAPPENED, offsetof(struct paca_struct, > irq_happened)); #ifdef CONFIG_PPC_BOOK3S > - DEFINE(PACACONTEXTID, offsetof(struct paca_struct, > context.id)); > + DEFINE(PACACONTEXTID, offsetof(struct paca_struct, > context_id)); #ifdef CONFIG_PPC_MM_SLICES > DEFINE(PACALOWSLICESPSIZE, offsetof(struct paca_struct, > - > context.low_slices_psize)); > + > context_low_slices_psize)); DEFINE(PACAHIGHSLICEPSIZE, > offsetof(struct paca_struct, > - > context.high_slices_psize)); > + > context_high_slices_psize)); DEFINE(MMUPSIZEDEFSIZE, sizeof(struct > mmu_psize_def)); #endif /* CONFIG_PPC_MM_SLICES */ > #endif > @@ -224,7 +224,7 @@ int main(void) > #ifdef CONFIG_PPC_MM_SLICES > DEFINE(MMUPSIZESLLP, offsetof(struct mmu_psize_def, sllp)); > #else > - DEFINE(PACACONTEXTSLLP, offsetof(struct paca_struct, > context.sllp)); > + DEFINE(PACACONTEXTSLLP, offsetof(struct paca_struct, > context_sllp)); #endif /* CONFIG_PPC_MM_SLICES */ > DEFINE(PACA_EXGEN, offsetof(struct paca_struct, exgen)); > DEFINE(PACA_EXMC, offsetof(struct paca_struct, exmc)); > diff --git a/arch/powerpc/mm/hash_utils_64.c > b/arch/powerpc/mm/hash_utils_64.c index fa62eb0..0e087e4 100644 > --- a/arch/powerpc/mm/hash_utils_64.c > +++ b/arch/powerpc/mm/hash_utils_64.c > @@ -877,11 +877,11 @@ static unsigned int get_paca_psize(unsigned > long addr) unsigned long index, mask_index; > > if (addr < SLICE_LOW_TOP) { > - lpsizes = get_paca()->context.low_slices_psize; > + lpsizes = get_paca()->context_low_slices_psize; > index = GET_LOW_SLICE_INDEX(addr); > return (lpsizes >> (index * 4)) & 0xF; > } > - hpsizes = get_paca()->context.high_slices_psize; > + hpsizes = get_paca()->context_high_slices_psize; > index = GET_HIGH_SLICE_INDEX(addr); > mask_index = index & 0x1; > return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xF; _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
