Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034241AbcJTRcV (ORCPT ); Thu, 20 Oct 2016 13:32:21 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50849 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1034167AbcJTRbs (ORCPT ); Thu, 20 Oct 2016 13:31:48 -0400 From: Pan Xinhui To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, xen-devel-request@lists.xenproject.org, kvm@vger.kernel.org Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com, bsingharora@gmail.com, boqun.feng@gmail.com, borntraeger@de.ibm.com, rkrcmar@redhat.com, Pan Xinhui Subject: [PATCH v5 6/9] x86, kvm: support vcpu preempted check Date: Thu, 20 Oct 2016 17:27:51 -0400 X-Mailer: git-send-email 2.4.11 In-Reply-To: <1476998874-2089-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> References: <1476998874-2089-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16102017-0052-0000-0000-000001DD4095 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16102017-0053-0000-0000-00000708D8CA Message-Id: <1476998874-2089-7-git-send-email-xinhui.pan@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-10-20_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1610200314 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3915 Lines: 115 Support the vcpu_is_preempted() functionality under KVM. This will enhance lock performance on overcommitted hosts (more runnable vcpus than physical cpus in the system) as doing busy waits for preempted vcpus will hurt system performance far worse than early yielding. Use one field of struct kvm_steal_time to indicate that if one vcpu is running or not. unix benchmark result: host: kernel 4.8.1, i5-4570, 4 cpus guest: kernel 4.8.1, 8 vcpus test-case after-patch before-patch Execl Throughput | 18307.9 lps | 11701.6 lps File Copy 1024 bufsize 2000 maxblocks | 1352407.3 KBps | 790418.9 KBps File Copy 256 bufsize 500 maxblocks | 367555.6 KBps | 222867.7 KBps File Copy 4096 bufsize 8000 maxblocks | 3675649.7 KBps | 1780614.4 KBps Pipe Throughput | 11872208.7 lps | 11855628.9 lps Pipe-based Context Switching | 1495126.5 lps | 1490533.9 lps Process Creation | 29881.2 lps | 28572.8 lps Shell Scripts (1 concurrent) | 23224.3 lpm | 22607.4 lpm Shell Scripts (8 concurrent) | 3531.4 lpm | 3211.9 lpm System Call Overhead | 10385653.0 lps | 10419979.0 lps Signed-off-by: Pan Xinhui --- arch/x86/include/uapi/asm/kvm_para.h | 3 ++- arch/x86/kernel/kvm.c | 12 ++++++++++++ arch/x86/kvm/x86.c | 18 ++++++++++++++++++ 3 files changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 94dc8ca..b3fec56 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -45,7 +45,8 @@ struct kvm_steal_time { __u64 steal; __u32 version; __u32 flags; - __u32 pad[12]; + __u8 preempted; + __u32 pad[11]; }; #define KVM_STEAL_ALIGNMENT_BITS 5 diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index edbbfc8..0b48dd2 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -415,6 +415,15 @@ void kvm_disable_steal_time(void) wrmsr(MSR_KVM_STEAL_TIME, 0, 0); } +static bool kvm_vcpu_is_preempted(int cpu) +{ + struct kvm_steal_time *src; + + src = &per_cpu(steal_time, cpu); + + return !!src->preempted; +} + #ifdef CONFIG_SMP static void __init kvm_smp_prepare_boot_cpu(void) { @@ -471,6 +480,9 @@ void __init kvm_guest_init(void) if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { has_steal_clock = 1; pv_time_ops.steal_clock = kvm_steal_clock; +#ifdef CONFIG_PARAVIRT_SPINLOCKS + pv_lock_ops.vcpu_is_preempted = kvm_vcpu_is_preempted; +#endif } if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6c633de..a627537 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2057,6 +2057,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu) &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) return; + vcpu->arch.st.steal.preempted = 0; + if (vcpu->arch.st.steal.version & 1) vcpu->arch.st.steal.version += 1; /* first time write, random junk */ @@ -2810,8 +2812,24 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); } +static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) +{ + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) + return; + + if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime, + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) + return; + + vcpu->arch.st.steal.preempted = 1; + + kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime, + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)); +} + void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) { + kvm_steal_time_set_preempted(vcpu); kvm_x86_ops->vcpu_put(vcpu); kvm_put_guest_fpu(vcpu); vcpu->arch.last_host_tsc = rdtsc(); -- 2.4.11