| Message ID | ad93acf5318c404683f5654d6734316e@BL2FFO11FD047.protection.gbl (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Ping! Anything I need to do or send to to get a merge on this? Regards, Peter On Tue, Mar 3, 2015 at 12:49 AM, Peter Crosthwaite <peter.crosthwaite@xilinx.com> wrote: > ARM64 has the yield nop hint which has the intended semantics of > cpu_relax. Implement. > > The immediate application is ARM CPU emulators. An emulator can take > advantage of the yield hint to de-prioritise an emulated CPU in favor > of other emulation tasks. QEMU A64 SMP emulation has yield awareness, > and sees a significant boot time performance increase with this change. > > Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com> > Acked-by: Will Deacon <will.deacon@arm.com> > --- > arch/arm64/include/asm/processor.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index f9be30e..ac2381d 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -126,7 +126,11 @@ extern void release_thread(struct task_struct *); > > unsigned long get_wchan(struct task_struct *p); > > -#define cpu_relax() barrier() > +static inline void cpu_relax(void) > +{ > + asm volatile("yield" ::: "memory"); > +} > + > #define cpu_relax_lowlatency() cpu_relax() > > /* Thread switching */ > -- > 2.3.0.1.g27a12f1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Wed, Mar 25, 2015 at 09:58:26AM +0000, Peter Crosthwaite wrote: > Ping! > > Anything I need to do or send to to get a merge on this? It's queued for 4.1 and should already be in linux-next. Cheers, Will
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index f9be30e..ac2381d 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -126,7 +126,11 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); -#define cpu_relax() barrier() +static inline void cpu_relax(void) +{ + asm volatile("yield" ::: "memory"); +} + #define cpu_relax_lowlatency() cpu_relax() /* Thread switching */