Re: [Qemu-ppc] [RFC PATCH 12/17] PowerPC: booke64: Add DO_KVM kernel hooks

[Alexander Graf]

On 12.07.2012, at 00:43, Benjamin Herrenschmidt wrote:

> On Thu, 2012-07-12 at 00:35 +0200, Alexander Graf wrote:
>>> On Thu, 2012-07-12 at 00:25 +0200, Alexander Graf wrote:
>>>> Or just free up another register early on, like here.
>>> 
>>> If you're going to do that, you want to measure the impact on null
>>> syscall performance though.
>> 
>> That should hold true for any change in that code, no?
> 
> Yes, but adding a gpr save is more invasive (you have to also load it
> back later on & put it on the stack).

What's the usual cache line size like on these boxes? If you align it properly 
with r10 and r11 on the paca so that all 3 registers are in the same cache 
line, the load should be almost for free, no?


Alex