From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37381C43460 for ; Mon, 17 May 2021 14:01:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1745F6109F for ; Mon, 17 May 2021 14:01:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237706AbhEQOC7 (ORCPT ); Mon, 17 May 2021 10:02:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237645AbhEQOCw (ORCPT ); Mon, 17 May 2021 10:02:52 -0400 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C51EC06175F; Mon, 17 May 2021 07:01:35 -0700 (PDT) Received: by mail-pj1-x102e.google.com with SMTP id gm21so3719961pjb.5; Mon, 17 May 2021 07:01:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=tPPyKEGZVk5W3b/nB56WzLLuyaXrswVyUx1Ed/5o3O4=; b=atyrkP7BjqyHjY2IB7GyY0a5GmCwQFfhG0p/q6m54DEi0AY69wWhJgByPa8Y6nNmdy STirIna+BxQaUMp80+jQIflI7bvR3lrb3IdK++O4vUn80zYUvtsYDnLhGTDXlt9RiU64 DyI5GDe+q9nXiprQ/HGX4de5LDWHvkjuVJIsxM+wxN8pyMGGoyw45u1v7SnGxt+fPxW9 hA/B6NB8CIL/woWH3rS5X9cf0Pd3zvsHronm3N7st5cvEM2iAiwAxTuCEFqeOgnyBWcb FvGLmlHltyHvm/0v0zL6CD7AKbrDe68ov3uLQJaZh9oMAchqii2cqkJtSEEtTXy1mdYS Y35w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=tPPyKEGZVk5W3b/nB56WzLLuyaXrswVyUx1Ed/5o3O4=; b=NtcjQRIYnf0YTPuClgyD551zBeiIeU4B0GslxSVFwXh73+4lYywCrBiA/L5m9C8e4Q 7a0RtBNtpVd9XucIxCcQoT8/lS+HIV0QdZaKUP9oix2j4kBp4aey5x/3eMgA0Vhs6i0k mM755pFFbK4HwDQ77JCPVfd5RvJz1LugJXbbtkKGb9vaX0BKR+ef5Lxt86ecwJ7RGh/O 6kv6xF/dcK+U6VKU/Rc1slesktdHp6yEufFvYjm/iBjIYSINlBC2cz1b95GVUUSyIxJf LFPFMWeeQ/5UKnzIAiUrqRMZzqvQE8xd8fams5Tbl3KSECS1Aom1tWH4758+tajg1Lcq 37Rg== X-Gm-Message-State: AOAM532ib0hi8U3RNTsMLlc+JQfCop7UjLLg27DuK7N1a61zufaLlG1f 5ODaue4sx4PuUU6Ki0pY7EPEnjsDUvY= X-Google-Smtp-Source: ABdhPJzfvxgIpucSVaKIfaF+zi+C+hFNNk08SdZS9g9Piwygu4QotouqiXsKm/5X1dFpFRoTUqAnJg== X-Received: by 2002:a17:90a:4404:: with SMTP id s4mr91755pjg.218.1621260094856; Mon, 17 May 2021 07:01:34 -0700 (PDT) Received: from localhost.localdomain ([203.205.141.61]) by smtp.googlemail.com with ESMTPSA id k10sm3074229pfu.175.2021.05.17.07.01.31 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 May 2021 07:01:34 -0700 (PDT) From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: [PATCH v3 5/5] KVM: LAPIC: Narrow the timer latency between wait_lapic_expire and world switch Date: Mon, 17 May 2021 07:00:28 -0700 Message-Id: <1621260028-6467-5-git-send-email-wanpengli@tencent.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1621260028-6467-1-git-send-email-wanpengli@tencent.com> References: <1621260028-6467-1-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li Let's treat lapic_timer_advance_ns automatically tune 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 automatically tune logic. This patch reduces ~30+ cycles for kvm-unit-tests/tscdeadline-latency when testing busy waits. Signed-off-by: Wanpeng Li --- arch/x86/kvm/lapic.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index c0ebef560bd1..552d2acf89ab 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1598,11 +1598,12 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu) guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); apic->lapic_timer.advance_expire_delta = guest_tsc - tsc_deadline; - if (guest_tsc < tsc_deadline) - __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc); - if (lapic_timer_advance_dynamic) adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta); + + guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); + if (guest_tsc < tsc_deadline) + __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc); } void kvm_wait_lapic_expire(struct kvm_vcpu *vcpu) -- 2.25.1