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author | Anton Blanchard <anton@samba.org> | 2015-10-29 11:43:55 +1100 |
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committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-12-01 13:52:24 +1100 |
commit | 152d523e6307c7152f9986a542f873b5c5863937 (patch) | |
tree | de3b7ec6c667e368f922f2cc17bf7c1806ac28dd /arch/powerpc/include/asm/switch_to.h | |
parent | af72ab646a6bee724f190820e8f56497a5b635f0 (diff) | |
download | linux-stable-152d523e6307c7152f9986a542f873b5c5863937.tar.gz linux-stable-152d523e6307c7152f9986a542f873b5c5863937.tar.bz2 linux-stable-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/switch_to.h')
-rw-r--r-- | arch/powerpc/include/asm/switch_to.h | 11 |
1 files changed, 0 insertions, 11 deletions
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); |