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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 170B6C433EF for ; Sat, 9 Oct 2021 02:14:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F28E561078 for ; Sat, 9 Oct 2021 02:14:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244358AbhJICP5 (ORCPT ); Fri, 8 Oct 2021 22:15:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244222AbhJICPf (ORCPT ); Fri, 8 Oct 2021 22:15:35 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0515CC061797 for ; Fri, 8 Oct 2021 19:13:22 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id f8-20020a2585480000b02905937897e3daso15198405ybn.2 for ; Fri, 08 Oct 2021 19:13:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=iENfBAERukntPY2X5QGQTh9qzr8Td2a/eMmZN0gkPVI=; b=DzCx6d3mDseqABvdcGbaVVyn1eWP9DyM0ptlZC0Av6M11xsmwM4hDygp2I9SRsOTlD CaLslZ/5tpgFn7ZGK8Q+oAp/z+7Kry0ksTb1JHhzjTahq7Wh+o5eGwzQrJzYlowAOZ48 VNCB+jXgqhl1lAdIBlzi52PfjMMWOIp8/GrzMp+AjpBgmC/UstMbkG/AsaR/Zi/J2Jar o4OtrA3m//aakuHjWV9VK3H1BLYWwyP3onVfEMCmc4KxgicKakfGDgJSztgcePWQk2I1 bTHWhpYvVB73G/ZnG29ntm8kUxVEF6vAxFCPnskmCGo64vtpSvX8eFpV4pMmLiFClOgf jaMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=iENfBAERukntPY2X5QGQTh9qzr8Td2a/eMmZN0gkPVI=; b=cdwBLH6Yyv/N6nNzBOG9yNKAtHjuuRAjXyi5vCMqRC4wz8ErDbPP2UwoWnNSXwTyd5 Cr7e3ZqONDS8/evO+/17HQ3LoSsOtl7eyIBIwSAx70gRiujpBQwX+ZDPzPP7BJpLgQ1s tRAhhk/BXAdpAuxWGOuMMY+PbNJDSacWyE1/IAPJgkLvnT/0LytBohYssl+wDiohhd2x Qb/jefsUCFFZzfLsnA+KkXqSsB69QdYlPB8q20x89301KCFVdJOGKUmfMf6O9ki8muTT Iz8FB2DzE68lE4+S6ewgXobiel/jCY0V33+I3bLLEoXQ4UaYS3cdZSrpNlWxny0PMyms k9Zg== X-Gm-Message-State: AOAM533O34oIsj8x+AE0xhyo0jdB1eKYxoRg1TrvGZYC/Z3gBlLqjDjD AuNJ87P0QMUb9ne9JSpJXdlIpURHZqk= X-Google-Smtp-Source: ABdhPJzWNw6k/Tym0AlNYDL00dpB0fqVjcBxlLLKgA5wVnQqHXg+hyQOuiK3gpCLlIvGNpb1Xv6thLhfBP8= X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:90:200:e39b:6333:b001:cb]) (user=seanjc job=sendgmr) by 2002:a25:bb93:: with SMTP id y19mr7661688ybg.266.1633745601224; Fri, 08 Oct 2021 19:13:21 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 8 Oct 2021 19:12:09 -0700 In-Reply-To: <20211009021236.4122790-1-seanjc@google.com> Message-Id: <20211009021236.4122790-17-seanjc@google.com> Mime-Version: 1.0 References: <20211009021236.4122790-1-seanjc@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v2 16/43] KVM: Don't redo ktime_get() when calculating halt-polling stop/deadline From: Sean Christopherson To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Calculate the halt-polling "stop" time using "cur" instead of redoing ktime_get(). In the happy case where hardware correctly predicts do_halt_poll, "cur" is only a few cycles old. And if the branch is mispredicted, arguably that extra latency should count toward the halt-polling time. In all likelihood, the numbers involved are in the noise and either approach is perfectly ok. Reviewed-by: David Matlack Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a36ccdc93a72..481e8178b43d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3272,7 +3272,7 @@ void kvm_vcpu_halt(struct kvm_vcpu *vcpu) start = cur = poll_end = ktime_get(); if (do_halt_poll) { - ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns); + ktime_t stop = ktime_add_ns(cur, vcpu->halt_poll_ns); do { /* -- 2.33.0.882.g93a45727a2-goog