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Date: Fri, 14 Oct 2016 13:11:58 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Wanpeng Li <kernellwp@...il.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org> Cc: Radim Krčmář <rkrcmar@...hat.com>, Yunhong Jiang <yunhong.jiang@...el.com>, Wanpeng Li <wanpeng.li@...mail.com> Subject: Re: [PATCH RFC V3 0/6] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support On 14/10/2016 12:05, Wanpeng Li wrote: > 2016-10-13 19:34 GMT+08:00 Wanpeng Li <kernellwp@...il.com>: > [...] >> >> The patchset reduces ~300+ clock cycles for each APIC timer oneshot mode >> operation virtualization. However, the performance of periodic mode is >> still bad, so this version is still a RFC. Your comments to improve the >> patchset is a great appreciated. > > I observed that the clock cycles between the start of > kvm_lapic_expired_hv_timer() (periodic mode emulated through restart a > preemption timer after the last preemption timer vmexit) to > kvm_inject_apic_timer_irqs() is almost half of the clock cycles > between the start of apic_timer_fn() (periodic mode emulated through > hrtimer) to kvm_inject_apic_timers_irqs(), so the overhead of > preemption timer is lower in this path. Maybe something is still not > correct in other places which results in performance of periodic mode > emulated by VMX preemption timer is still not good. Any help is a > great appreciated. :) > > Radim, Paolo, ping :) Just post the patches and we'll see. :) Another useful thing to do is to prepare testcases similar to tscdeadline_latency, but using the periodic and oneshot modes. Paolo
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