Re: [PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
From: Peter Zijlstra <peterz@infradead.org>
Date: 2014-06-15 13:17:13
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kvm, linux-arch, lkml
On Thu, Jun 12, 2014 at 04:48:41PM -0400, Waiman Long wrote:
I don't have a good understanding of the kernel alternatives mechanism.
I didn't either; I do now, cost me a whole day reading up on alternative/paravirt code patching. See the patches I just send out; I got the 'native' case with paravirt enabled to be one NOP worse than the native case without paravirt -- for queue_spin_unlock. The lock slowpath is several nops and some pointless movs more expensive.