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| author | Anton Blanchard <anton@samba.org> | 2015-10-29 11:43:53 +1100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-12-01 13:52:24 +1100 |
| commit | 07e45c120c9c61b792be62182b0a8f706ee2ab24 (patch) | |
| tree | 5936a948a53b1bca0dad87eaa5c23648527a8970 /arch/powerpc/kernel/entry_64.S | |
| parent | 31a40e2b052c0f2b80df7b56928f9d5ff9c96933 (diff) | |
| download | op-kernel-dev-07e45c120c9c61b792be62182b0a8f706ee2ab24.zip op-kernel-dev-07e45c120c9c61b792be62182b0a8f706ee2ab24.tar.gz | |
powerpc: Don't disable kernel FP/VMX/VSX MSR bits on context switch
Writing the MSR is slow, so we want to avoid it whenever possible.
A subsequent patch will add a debug option that strictly manages the
FP/VMX/VSX unavailable bits. For now just remove it, matching what
we do in other areas of the kernel (eg enable_kernel_altivec()).
A context switch microbenchmark using yield():
http://ozlabs.org/~anton/junkcode/context_switch2.c
./context_switch2 --test=yield --fp 0 0
shows an improvement of almost 3% on POWER8.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 15 |
1 files changed, 1 insertions, 14 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index a94f155..93bb284 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -453,26 +453,13 @@ _GLOBAL(_switch) SAVE_8GPRS(14, r1) SAVE_10GPRS(22, r1) mflr r20 /* Return to switch caller */ - mfmsr r22 - li r0, MSR_FP -#ifdef CONFIG_VSX -BEGIN_FTR_SECTION - oris r0,r0,MSR_VSX@h /* Disable VSX */ -END_FTR_SECTION_IFSET(CPU_FTR_VSX) -#endif /* CONFIG_VSX */ #ifdef CONFIG_ALTIVEC BEGIN_FTR_SECTION - oris r0,r0,MSR_VEC@h /* Disable altivec */ mfspr r24,SPRN_VRSAVE /* save vrsave register value */ std r24,THREAD_VRSAVE(r3) END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC) #endif /* CONFIG_ALTIVEC */ - and. r0,r0,r22 - beq+ 1f - andc r22,r22,r0 - MTMSRD(r22) - isync -1: std r20,_NIP(r1) + std r20,_NIP(r1) mfcr r23 std r23,_CCR(r1) std r1,KSP(r3) /* Set old stack pointer */ |
