Messages in this thread | | | Date | Tue, 24 Oct 2017 13:18:59 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH 1/1] locking/qspinlock/x86: Avoid test-and-set when PV_DEDICATED is set |
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2017-10-23 17:44-0700, Eduardo Valentin: > Currently, the existing qspinlock implementation will fallback to > test-and-set if the hypervisor has not set the PV_UNHALT flag.
Where have you detected the main source of overhead with pinned VCPUs? Makes me wonder if we couldn't improve general PV_UNHALT,
thanks.
> This patch gives the opportunity to guest kernels to select > between test-and-set and the regular queueu fair lock implementation > based on the PV_DEDICATED KVM feature flag. When the PV_DEDICATED > flag is not set, the code will still fall back to test-and-set, > but when the PV_DEDICATED flag is set, the code will use > the regular queue spinlock implementation.
Some flag makes sense and we do want to make sure that userspaces don't enable it in pass-through-cpuid mode.
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