diff options
| author | Anton Blanchard <anton@samba.org> | 2015-10-29 01:43:55 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-12-01 03:52:24 +0100 |
| commit | 152d523e6307c7152f9986a542f873b5c5863937 (patch) | |
| tree | de3b7ec6c667e368f922f2cc17bf7c1806ac28dd /arch/powerpc/include/asm | |
| parent | powerpc: Don't disable MSR bits in do_load_up_transact_*() functions (diff) | |
| download | linux-152d523e6307c7152f9986a542f873b5c5863937.tar.xz linux-152d523e6307c7152f9986a542f873b5c5863937.zip | |
powerpc: Create context switch helpers save_sprs() and restore_sprs()
Move all our context switch SPR save and restore code into two
helpers. We do a few optimisations:
- Group all mfsprs and all mtsprs. In many cases an mtspr sets a
scoreboarding bit that an mfspr waits on, so the current practise of
mfspr A; mtspr A; mfpsr B; mtspr B is the worst scheduling we can
do.
- SPR writes are slow, so check that the value is changing before
writing it.
A context switch microbenchmark using yield():
http://ozlabs.org/~anton/junkcode/context_switch2.c
./context_switch2 --test=yield 0 0
shows an improvement of almost 10% on POWER8.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/include/asm')
| -rw-r--r-- | arch/powerpc/include/asm/processor.h | 1 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/switch_to.h | 11 |
2 files changed, 1 insertions, 11 deletions
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index 5afea361beaa..c273f3e0ba84 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -294,6 +294,7 @@ struct thread_struct { #endif #ifdef CONFIG_PPC64 unsigned long dscr; + unsigned long fscr; /* * This member element dscr_inherit indicates that the process * has explicitly attempted and changed the DSCR register value diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h index 15cca17cba4b..33a071d24ba8 100644 --- a/arch/powerpc/include/asm/switch_to.h +++ b/arch/powerpc/include/asm/switch_to.h @@ -15,17 +15,6 @@ extern struct task_struct *__switch_to(struct task_struct *, struct thread_struct; extern struct task_struct *_switch(struct thread_struct *prev, struct thread_struct *next); -#ifdef CONFIG_PPC_BOOK3S_64 -static inline void save_early_sprs(struct thread_struct *prev) -{ - if (cpu_has_feature(CPU_FTR_ARCH_207S)) - prev->tar = mfspr(SPRN_TAR); - if (cpu_has_feature(CPU_FTR_DSCR)) - prev->dscr = mfspr(SPRN_DSCR); -} -#else -static inline void save_early_sprs(struct thread_struct *prev) {} -#endif extern void enable_kernel_fp(void); extern void enable_kernel_altivec(void); |