From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751796Ab1AEJkK (ORCPT ); Wed, 5 Jan 2011 04:40:10 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:52775 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751653Ab1AEJkI (ORCPT ); Wed, 5 Jan 2011 04:40:08 -0500 Message-ID: <4D243C7B.8060205@cn.fujitsu.com> Date: Wed, 05 Jan 2011 17:40:11 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Thunderbird/3.1.7 MIME-Version: 1.0 To: Avi Kivity CC: Marcelo Tosatti , LKML , KVM Subject: [PATCH 3/3] KVM: make make_all_cpus_request() lockless References: <4D243B95.3070203@cn.fujitsu.com> In-Reply-To: <4D243B95.3070203@cn.fujitsu.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-01-05 17:39:48, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-01-05 17:39:48, Serialize complete at 2011-01-05 17:39:48 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now, we have 'vcpu->guest_mode' to judge whether need to send ipi to other cpus, this way is very exact, so checking request bit is needless, then we can drop the spinlock let it's collateral There is the simple test result of kernbench: before patch: real 5m5.100s user 3m58.051s sys 9m4.742s real 5m3.443s user 3m58.837s sys 9m6.007s after patch: real 5m0.769s user 3m59.666s sys 8m41.406s real 4m57.980s user 3m59.302s sys 8m38.916s Signed-off-by: Xiao Guangrong --- include/linux/kvm_host.h | 6 ------ virt/kvm/kvm_main.c | 9 +++------ 2 files changed, 3 insertions(+), 12 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index b5021db..3e64133 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -212,7 +212,6 @@ struct kvm_memslots { struct kvm { spinlock_t mmu_lock; - raw_spinlock_t requests_lock; struct mutex slots_lock; struct mm_struct *mm; /* userspace tied to this vm */ struct kvm_memslots *memslots; @@ -719,11 +718,6 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) set_bit(req, &vcpu->requests); } -static inline bool kvm_make_check_request(int req, struct kvm_vcpu *vcpu) -{ - return test_and_set_bit(req, &vcpu->requests); -} - static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) { if (test_bit(req, &vcpu->requests)) { diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6648c6e..34066ab 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -147,11 +147,9 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) zalloc_cpumask_var(&cpus, GFP_ATOMIC); - raw_spin_lock(&kvm->requests_lock); - me = smp_processor_id(); + me = get_cpu(); kvm_for_each_vcpu(i, vcpu, kvm) { - if (kvm_make_check_request(req, vcpu)) - continue; + kvm_make_request(req, vcpu); cpu = vcpu->cpu; if (cpus != NULL && cpu != -1 && cpu != me && atomic_read(&vcpu->guest_mode)) @@ -163,7 +161,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) smp_call_function_many(cpus, ack_flush, NULL, 1); else called = false; - raw_spin_unlock(&kvm->requests_lock); + put_cpu(); free_cpumask_var(cpus); return called; } @@ -429,7 +427,6 @@ static struct kvm *kvm_create_vm(void) kvm->mm = current->mm; atomic_inc(&kvm->mm->mm_count); spin_lock_init(&kvm->mmu_lock); - raw_spin_lock_init(&kvm->requests_lock); kvm_eventfd_init(kvm); mutex_init(&kvm->lock); mutex_init(&kvm->irq_lock); -- 1.7.3.4