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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id u23sm2943943pfn.106.2021.05.18.12.14.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 May 2021 12:14:01 -0700 (PDT) Date: Tue, 18 May 2021 19:13:58 +0000 From: Sean Christopherson To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: [PATCH v4 5/5] KVM: LAPIC: Narrow the timer latency between wait_lapic_expire and world switch Message-ID: References: <1621339235-11131-1-git-send-email-wanpengli@tencent.com> <1621339235-11131-5-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1621339235-11131-5-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 18, 2021, Wanpeng Li wrote: > From: Wanpeng Li > > Let's treat lapic_timer_advance_ns automatic tuning logic as hypervisor > overhead, move it before wait_lapic_expire instead of between wait_lapic_expire > and the world switch, the wait duration should be calculated by the > up-to-date guest_tsc after the overhead of automatic tuning logic. This > patch reduces ~30+ cycles for kvm-unit-tests/tscdeadline-latency when testing > busy waits. > > Signed-off-by: Wanpeng Li > --- Reviewed-by: Sean Christopherson