Messages in this thread | | | Date | Wed, 25 Feb 2015 13:24:38 +0000 | From | Will Deacon <> | Subject | Re: [RFC PATCH] arm64: Implement cpu_relax as yield |
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On Tue, Feb 24, 2015 at 11:07:37PM +0000, Peter Crosthwaite 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.
Could you elaborate on the QEMU SMP boot case please? Usually SMP pens for booting make use of wfe/sev to minimise the spinning overhead.
Will
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