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authorNir Weiner <nir.weiner@oracle.com>2019-01-27 12:17:15 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2019-02-20 22:48:50 +0100
commit49113d360bdeb4dd916fb6bffbcc3e157422b6fd (patch)
tree9580d0cf4466aac62107b063a73cf3de6885943f /arch/x86/kernel
parent7fa08e71b4a0591a518814fa78b32e124f90d587 (diff)
KVM: Expose the initial start value in grow_halt_poll_ns() as a module parameter
The hard-coded value 10000 in grow_halt_poll_ns() stands for the initial start value when raising up vcpu->halt_poll_ns. It actually sets the first timeout to the first polling session. This value has significant effect on how tolerant we are to outliers. On the standard case, higher value is better - we will spend more time in the polling busyloop, handle events/interrupts faster and result in better performance. But on outliers it puts us in a busy loop that does nothing. Even if the shrink factor is zero, we will still waste time on the first iteration. The optimal value changes between different workloads. It depends on outliers rate and polling sessions length. As this value has significant effect on the dynamic halt-polling algorithm, it should be configurable and exposed. Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Liran Alon <liran.alon@oracle.com> Signed-off-by: Nir Weiner <nir.weiner@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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