From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933992Ab3BMMMW (ORCPT ); Wed, 13 Feb 2013 07:12:22 -0500 Received: from terminus.zytor.com ([198.137.202.10]:36616 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933905Ab3BMMMU (ORCPT ); Wed, 13 Feb 2013 07:12:20 -0500 Date: Wed, 13 Feb 2013 04:10:53 -0800 From: tip-bot for Rik van Riel Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, a.p.zijlstra@chello.nl, torvalds@linux-foundation.org, riel@redhat.com, raghavendra.kt@linux.vnet.ibm.com, akpm@linux-foundation.org, chegu_vinod@hp.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, a.p.zijlstra@chello.nl, riel@redhat.com, raghavendra.kt@linux.vnet.ibm.com, akpm@linux-foundation.org, chegu_vinod@hp.com, tglx@linutronix.de In-Reply-To: <20130207162449.0292685a@cuia.bos.redhat.com> References: <20130207162449.0292685a@cuia.bos.redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/locking] x86/smp: Limit spinlock delay on virtual machines Git-Commit-ID: 12b682864a336d72bfd507244649bd1066d90e43 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Wed, 13 Feb 2013 04:10:59 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 12b682864a336d72bfd507244649bd1066d90e43 Gitweb: http://git.kernel.org/tip/12b682864a336d72bfd507244649bd1066d90e43 Author: Rik van Riel AuthorDate: Thu, 7 Feb 2013 16:24:49 -0500 Committer: Ingo Molnar CommitDate: Wed, 13 Feb 2013 09:07:21 +0100 x86/smp: Limit spinlock delay on virtual machines Modern Intel and AMD CPUs will trap to the host when the guest is spinning on a spinlock, allowing the host to schedule in something else. This effectively means the host is taking care of spinlock backoff for virtual machines. It also means that doing the spinlock backoff in the guest anyway can lead to totally unpredictable results, extremely large backoffs, and performance regressions. To prevent those problems, we limit the spinlock backoff delay, when running in a virtual machine, to a small value. Signed-off-by: Rik van Riel Reviewed-by: Raghavendra K T Cc: aquini@redhat.com Cc: eric.dumazet@gmail.com Cc: lwoodman@redhat.com Cc: knoel@redhat.com Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20130207162449.0292685a@cuia.bos.redhat.com Signed-off-by: Ingo Molnar Tested-by: Chegu Vinod --- arch/x86/include/asm/processor.h | 2 ++ arch/x86/kernel/cpu/hypervisor.c | 2 ++ arch/x86/kernel/smp.c | 21 +++++++++++++++++++-- 3 files changed, 23 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 888184b..2856972 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -158,9 +158,11 @@ extern __u32 cpu_caps_set[NCAPINTS]; #ifdef CONFIG_SMP DECLARE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info); #define cpu_data(cpu) per_cpu(cpu_info, cpu) +extern void init_guest_spinlock_delay(void); #else #define cpu_info boot_cpu_data #define cpu_data(cpu) boot_cpu_data +static inline void init_guest_spinlock_delay(void) {} #endif extern const struct seq_operations cpuinfo_op; diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c index a8f8fa9..4a53724 100644 --- a/arch/x86/kernel/cpu/hypervisor.c +++ b/arch/x86/kernel/cpu/hypervisor.c @@ -76,6 +76,8 @@ void __init init_hypervisor_platform(void) init_hypervisor(&boot_cpu_data); + init_guest_spinlock_delay(); + if (x86_hyper->init_platform) x86_hyper->init_platform(); } diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 8e94469..73be656 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -116,8 +116,25 @@ static bool smp_no_nmi_ipi = false; #define DELAY_SHIFT 8 #define DELAY_FIXED_1 (1<> DELAY_SHIFT;