| Message ID | 1446079451-8774-2-git-send-email-anton@samba.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Thu, 2015-29-10 at 00:43:53 UTC, Anton Blanchard wrote: > 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> Applied all 19 patches to powerpc next, thanks. http://git.kernel.org/cgit/linux/kernel/git/powerpc/linux.git/log/?h=next cheers
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 */
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> --- arch/powerpc/kernel/entry_64.S | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)