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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
