On 09/06/2017 09:06 AM, Peter Zijlstra wrote: > On Wed, Sep 06, 2017 at 08:44:09AM -0400, Waiman Long wrote: >> On 09/06/2017 03:08 AM, Peter Zijlstra wrote: >>> Guys, please trim email. >>> >>> On Tue, Sep 05, 2017 at 10:31:46AM -0400, Waiman Long wrote: >>>> For clarification, I was actually asking if you consider just adding one >>>> more jump label to skip it for Xen/KVM instead of making >>>> virt_spin_lock() a pv-op. >>> I don't understand. What performance are you worried about. Native will >>> now do: "xor rax,rax; jnz some_cold_label" that's fairly trival code. >> It is not native that I am talking about. I am worry about VM with >> non-Xen/KVM hypervisor where virt_spin_lock() will actually be called. >> Now that function will become a callee-saved function call instead of >> being inlined into the native slowpath function. > But only if we actually end up using the test-and-set thing, because if > you have paravirt we end up using that. I am talking about scenario like a kernel with paravirt spinlock running in a VM managed by VMware, for example. We may not want to penalize them while there are alternatives with less penalty. Cheers, Longman _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
