cpuidle: haltpoll: do not shrink guest poll_limit_ns below grow_start
While adjusting guest halt poll limit, grow block starts at guest_halt_poll_grow_start without taking intermediate values. Similar behavior is expected while shrinking the value. This avoids short interval values which are really not required. VCPU1 trace (guest_halt_poll_shrink equals 2): VCPU1 grow 10000 VCPU1 shrink 5000 VCPU1 shrink 2500 VCPU1 shrink 1250 VCPU1 shrink 625 VCPU1 shrink 312 VCPU1 shrink 156 VCPU1 shrink 78 VCPU1 shrink 39 VCPU1 shrink 19 VCPU1 shrink 9 VCPU1 shrink 4 Similar change is done in KVM halt poll flow with below patch: Link: https://lore.kernel.org/kvm/20211006133021.271905-3-sashal@kernel.org/ Co-developed-by: Rajendran Jaishankar <jaishankar.rajendran@intel.com> Signed-off-by: Rajendran Jaishankar <jaishankar.rajendran@intel.com> Signed-off-by: Parshuram Sangle <parshuram.sangle@intel.com> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> [ rjw: Subject edits ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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@ -98,10 +98,15 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
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unsigned int shrink = guest_halt_poll_shrink;
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val = dev->poll_limit_ns;
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if (shrink == 0)
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if (shrink == 0) {
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val = 0;
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else
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} else {
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val /= shrink;
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/* Reset value to 0 if shrunk below grow_start */
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if (val < guest_halt_poll_grow_start)
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val = 0;
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}
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trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);
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dev->poll_limit_ns = val;
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}
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