From patchwork Sat Sep 25 00:55:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 1532609 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20210112 header.b=SfLacDGD; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=kvm-ppc-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4HGVq76v3Jz9sW8 for ; Sat, 25 Sep 2021 10:57:07 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346490AbhIYA6h (ORCPT ); Fri, 24 Sep 2021 20:58:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346911AbhIYA6V (ORCPT ); Fri, 24 Sep 2021 20:58:21 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC3CDC0617BB for ; Fri, 24 Sep 2021 17:55:57 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id s10-20020a05621406aa00b003821a333809so23915125qvz.21 for ; Fri, 24 Sep 2021 17:55:57 -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=5cNFroYBSThqqpJCYxzBjAkytlwovA+rbtWpXsyqDeo=; b=SfLacDGDPv0O+ce1feGYy7BDlJVOIPkrwFpJqoWdePykloL2O82WlaKRzOwLeffojV WekB5mzNRTsRAE7CDSxzp55a5GlHpqh/h04E/0Cqn+9co39zSHc1rwlgwjHIm0Eq+/g1 rLsDyI7TI6ImRbwiTwKX0t1Q8ZQyoCYrzRYyQ4Xqwn0rlAUNh8TrYEq/em7hwrNonrfc Au70p/9HXYWVD3oyP35n9WXZarKqfxjjLGSen8K95241TMcO649zTLMZSD1UsjUAj//k JNR5GrbIoX2CF5HqJzqUR8/mcVQlOI2NUabeIFYhUNE1yZiL3ZPJAKN3+lQsuLE7ow/b sO3A== 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=5cNFroYBSThqqpJCYxzBjAkytlwovA+rbtWpXsyqDeo=; b=QdxHTZxWc3WEyZShxUrEW82MHPEeSSUND98A5vsmhTDwfDr+Hr7M/aJnsf/KODHMsC /TeRERvrHXivsl0dwuJ0o3DySwOVzr91oaYoObXUXlYuZ0hp+Hc68sRqKPsTaveGON7X FtUuTg+HVs5BwKRQVzD0VUGkvZygpqnftT4pcJ1nF4b/TIZAlSKUJAnIf5c2uvLWp0F2 B7LrEgA1C/7bZxaBNN4sU4qhX39BSem3XrJlpBt43TSQ74wwS1GNIoJJqtJtBAWqhczQ CiNAtG2FCm4Te2xhu4ZK8X5LwmSGzSrxYHqcq/zdmMELCmq9leVFpUx8jLiO7XQGKTcS GIAg== X-Gm-Message-State: AOAM533XJ68ZmzGqWoDj5T+rqktMHxInKaJ6KT2/AJdmG2CDUkdH7AXB Qt6In/F+kS1Y47LVcDtUwbv26Rj3SWM= X-Google-Smtp-Source: ABdhPJwTW1UybwFgg5M8F4nzh531Ub5JbtN0jF/yWxCBJfUYuvXgy/++XZQV+BSuMlLfxb0INGVd0hW95rg= X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:90:200:4c72:89be:dba3:2bcb]) (user=seanjc job=sendgmr) by 2002:a05:6214:148b:: with SMTP id bn11mr13269187qvb.67.1632531356963; Fri, 24 Sep 2021 17:55:56 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 24 Sep 2021 17:55:26 -0700 In-Reply-To: <20210925005528.1145584-1-seanjc@google.com> Message-Id: <20210925005528.1145584-13-seanjc@google.com> Mime-Version: 1.0 References: <20210925005528.1145584-1-seanjc@google.com> X-Mailer: git-send-email 2.33.0.685.g46640cef36-goog Subject: [PATCH 12/14] KVM: Don't redo ktime_get() when calculating halt-polling stop/deadline From: Sean Christopherson To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , 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, linux-kernel@vger.kernel.org, David Matlack , Jing Zhang Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@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. Signed-off-by: Sean Christopherson Reviewed-by: David Matlack --- 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 2980d2b88559..80f78daa6b8d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3267,7 +3267,7 @@ 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 { /*