On Fri, Sep 04, 2015 at 08:58:38AM -0700, Linus Torvalds wrote: > On Fri, Sep 4, 2015 at 8:30 AM, Peter Zijlstra <pet...@infradead.org> wrote: > >> And even ignoring the "implementation was crap" issue, some people may > >> well want their kernels to be "bare hardware" kernels even under a > >> hypervisor. It may be a slim hypervisor that gives you all the cpus, > >> or it may just be a system that is just sufficiently overprovisioned, > >> so you don't get vcpu preemption in practice. > > > > Fair enough; I had not considered the slim hypervisor case. > > > > Should I place the virt_spin_lock() thing under CONFIG_PARAVIRT (maybe > > even _SPINLOCKS) such that only paravirt enabled kernels when ran on a > > hypervisor that does not support paravirt patching (HyperV, VMware, > > etc..) revert to the test-and-set? > > My gut feel would be to try to match out old paravirt setup, which > similarly replaced the ticket locks with the test-and-set lock, and > try to match the situation where that happened?
I'm not sure there was a test-and-set option in 4.1. Either the hypervisor layer implemented paravirt spinlocks (Xen, KVM) (and you selected CONFIG_PARAVIRT_SPINLOCKS, which had a fairly large negative impact on native code), or you got our native locking. So if you want I can simply remove the whole test-and-set thing, but I'd rather fix it and put it under one of the PARAVIRT options. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
