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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 0971AC04AAC for ; Mon, 20 May 2019 11:22:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1C822081C for ; Mon, 20 May 2019 11:22:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kzFA2iZk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732691AbfETLW4 (ORCPT ); Mon, 20 May 2019 07:22:56 -0400 Received: from mail-oi1-f195.google.com ([209.85.167.195]:43684 "EHLO mail-oi1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731487AbfETLW4 (ORCPT ); Mon, 20 May 2019 07:22:56 -0400 Received: by mail-oi1-f195.google.com with SMTP id t187so9647689oie.10; Mon, 20 May 2019 04:22:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=pqJsM3I7VCsCBoW08AaOqNI2KyFITesPxcJ79o2nhOY=; b=kzFA2iZkmhj+hMC7x3NQTmHLxTdFCMkKG72QKILHzE5vC2f2S4rkZsgL983zr8+8BZ wTiDF+EPQdFWOpqI/XujsRnREJMf+i2r30eP2gDEyN68vKiFzWUYAG+3b0U7n29EAxMF Us2X9NgwH8z9Igvtc7iLkRAZLiZipZXqs96CFG9V+cdQWL6fvBiEEgH5Ye6UUWevD5FZ iIAjHVG31ilVJd8yio/TXoRFakMTusuYv3+4MQTGzRD20WcsPgKjzw2CTvCUb1ruSI2p 8Z87vggS/oxAneCCbsdv/rf3tJNm4UGq2Dy/RyPyq4USZfca50KZcfJNBxPhTtHsOcCC 2KvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=pqJsM3I7VCsCBoW08AaOqNI2KyFITesPxcJ79o2nhOY=; b=P/3YM0tR/XtC0P5iB/FGKSbM/cOocBxYhtKInW65WAZq4+UXpvaOLjfQT3eM63cCzX 3VaDcS1P18EyRK/OmeuBNdY4i03ZledelYrFfgC/DAvqJB7fbD2hWaq+areklByoZnX5 SOscHUwhte6Lo7cBhgZGQk6T2sAx2xg2Ts6oHC8CCfc6TJZUSfmR5duHh9pBntX7dDsB vfKsVUkU9XNZlA1953Nm7VvajmxAT8qAZKL8gxAxkOtabF2bAOnaGLXyCZMKSDntiltH 7EWEoZJxQBddg5rYEi7I0pattAwuUxfipPxb/2tfUbnRNPpGgMR6dPcrXOV2rBDdIHLs YrRg== X-Gm-Message-State: APjAAAXN4f1VOcVrrufn4iTft50fETyBSKZcUNbCEJUTBioBMuHL9nV0 86aZMASwJ5LMwtNF1q9n+e4kDHk/LfWwEmHq5dsj0wws X-Google-Smtp-Source: APXvYqzzzLEbFr/YCGl6P2GF59jY07tpiE2qxD8404B1NsnaV6x3z47aRMdPOBTHq8Sh9jE3FuwsMT4L1bi8SMBqPmM= X-Received: by 2002:aca:c711:: with SMTP id x17mr48064oif.174.1558351375321; Mon, 20 May 2019 04:22:55 -0700 (PDT) MIME-Version: 1.0 References: <1558340289-6857-1-git-send-email-wanpengli@tencent.com> <1558340289-6857-5-git-send-email-wanpengli@tencent.com> In-Reply-To: From: Wanpeng Li Date: Mon, 20 May 2019 19:22:46 +0800 Message-ID: Subject: Re: [PATCH v4 4/5] KVM: LAPIC: Delay trace advance expire delta To: Paolo Bonzini Cc: LKML , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Sean Christopherson , Liran Alon Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 20 May 2019 at 19:14, Paolo Bonzini wrote: > > On 20/05/19 10:18, Wanpeng Li wrote: > > From: Wanpeng Li > > > > wait_lapic_expire() call was moved above guest_enter_irqoff() because of > > its tracepoint, which violated the RCU extended quiescent state invoked > > by guest_enter_irqoff()[1][2]. This patch simply moves the tracepoint > > below guest_exit_irqoff() in vcpu_enter_guest(). Snapshot the delta before > > VM-Enter, but trace it after VM-Exit. This can help us to move > > wait_lapic_expire() just before vmentry in the later patch. > > > > [1] Commit 8b89fe1f6c43 ("kvm: x86: move tracepoints outside extended quiescent state") > > [2] https://patchwork.kernel.org/patch/7821111/ > > This is a bit confusing, since the delta is printed after the > corresponding vmexit but the wait is done before the vmentry. I think > we can drop the tracepoint: > > ------------- 8< ---------------- > From ae148d98d49b96b5222e2c78ac1b1e13cc526d71 Mon Sep 17 00:00:00 2001 > From: Paolo Bonzini > Date: Mon, 20 May 2019 13:10:01 +0200 > Subject: [PATCH] KVM: lapic: replace wait_lapic_expire tracepoint with > restart_apic_timer > > wait_lapic_expire() call was moved above guest_enter_irqoff() because of > its tracepoint, which violated the RCU extended quiescent state invoked > by guest_enter_irqoff()[1][2]. > > We would like to move wait_lapic_expire() just before vmentry, which would > place wait_lapic_expire() again inside the extended quiescent state. Drop > the tracepoint, but add instead another one that can be useful and where > we can check the status of the adaptive tuning procedure. https://lkml.org/lkml/2019/5/15/1435 Maybe Sean's comment is reasonable, per-vCPU debugfs entry for adaptive tuning and wait_lapic_expire() tracepoint for hand tuning. Regards, Wanpeng Li > > [1] Commit 8b89fe1f6c43 ("kvm: x86: move tracepoints outside extended quiescent state") > [2] https://patchwork.kernel.org/patch/7821111/ > > Signed-off-by: Paolo Bonzini > > --- > arch/x86/kvm/lapic.c | 4 +++- > arch/x86/kvm/trace.h | 15 +++++++-------- > 2 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index c12b090f4fad..8f05c1d0b486 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1545,7 +1545,6 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu) > tsc_deadline = apic->lapic_timer.expired_tscdeadline; > apic->lapic_timer.expired_tscdeadline = 0; > guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc()); > - trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline); > > if (guest_tsc < tsc_deadline) > __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc); > @@ -1763,6 +1762,9 @@ static void start_sw_timer(struct kvm_lapic *apic) > > static void restart_apic_timer(struct kvm_lapic *apic) > { > + trace_kvm_restart_apic_timer(apic->vcpu->vcpu_id, > + apic->lapic_timer.timer_advance_ns); > + > preempt_disable(); > > if (!apic_lvtt_period(apic) && atomic_read(&apic->lapic_timer.pending)) > diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h > index 4d47a2631d1f..f6e000038f3f 100644 > --- a/arch/x86/kvm/trace.h > +++ b/arch/x86/kvm/trace.h > @@ -953,24 +953,23 @@ > __entry->flags) > ); > > -TRACE_EVENT(kvm_wait_lapic_expire, > - TP_PROTO(unsigned int vcpu_id, s64 delta), > - TP_ARGS(vcpu_id, delta), > +TRACE_EVENT(kvm_restart_apic_timer, > + TP_PROTO(unsigned int vcpu_id, u32 advance), > + TP_ARGS(vcpu_id, advance), > > TP_STRUCT__entry( > __field( unsigned int, vcpu_id ) > - __field( s64, delta ) > + __field( u32, advance ) > ), > > TP_fast_assign( > __entry->vcpu_id = vcpu_id; > - __entry->delta = delta; > + __entry->advance = advance; > ), > > - TP_printk("vcpu %u: delta %lld (%s)", > + TP_printk("vcpu %u: advance %u", > __entry->vcpu_id, > - __entry->delta, > - __entry->delta < 0 ? "early" : "late") > + __entry->advance) > ); > > TRACE_EVENT(kvm_enter_smm,