From: Peter Zijlstra <peterz@infradead.org> To: Waiman Long <longman@redhat.com> Cc: "Jeremy Fitzhardinge" <jeremy@goop.org>, "Chris Wright" <chrisw@sous-sol.org>, "Alok Kataria" <akataria@vmware.com>, "Rusty Russell" <rusty@rustcorp.com.au>, "Ingo Molnar" <mingo@redhat.com>, "Thomas Gleixner" <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, "Pan Xinhui" <xinhui.pan@linux.vnet.ibm.com>, "Paolo Bonzini" <pbonzini@redhat.com>, "Radim Krčmář" <rkrcmar@redhat.com>, "Boris Ostrovsky" <boris.ostrovsky@oracle.com>, "Juergen Gross" <jgross@suse.com> Subject: Re: [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function Date: Fri, 10 Feb 2017 17:19:28 +0100 [thread overview] Message-ID: <20170210161928.GI6515@twins.programming.kicks-ass.net> (raw) In-Reply-To: <1486741389-8513-1-git-send-email-longman@redhat.com> On Fri, Feb 10, 2017 at 10:43:09AM -0500, Waiman Long wrote: > It was found when running fio sequential write test with a XFS ramdisk > on a VM running on a 2-socket x86-64 system, the %CPU times as reported > by perf were as follows: > > 69.75% 0.59% fio [k] down_write > 69.15% 0.01% fio [k] call_rwsem_down_write_failed > 67.12% 1.12% fio [k] rwsem_down_write_failed > 63.48% 52.77% fio [k] osq_lock > 9.46% 7.88% fio [k] __raw_callee_save___kvm_vcpu_is_preempt > 3.93% 3.93% fio [k] __kvm_vcpu_is_preempted > Thinking about this again, wouldn't something like the below also work? diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 099fcba4981d..6aa33702c15c 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -589,6 +589,7 @@ static void kvm_wait(u8 *ptr, u8 val) local_irq_restore(flags); } +#ifdef CONFIG_X86_32 __visible bool __kvm_vcpu_is_preempted(int cpu) { struct kvm_steal_time *src = &per_cpu(steal_time, cpu); @@ -597,6 +598,31 @@ __visible bool __kvm_vcpu_is_preempted(int cpu) } PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted); +#else + +extern bool __raw_callee_save___kvm_vcpu_is_preempted(int); + +asm( +".pushsection .text;" +".global __raw_callee_save___kvm_vcpu_is_preempted;" +".type __raw_callee_save___kvm_vcpu_is_preempted, @function;" +"__raw_callee_save___kvm_vcpu_is_preempted:" +FRAME_BEGIN +"push %rdi;" +"push %rdx;" +"movslq %edi, %rdi;" +"movq $steal_time+16, %rax;" +"movq __per_cpu_offset(,%rdi,8), %rdx;" +"cmpb $0, (%rdx,%rax);" +"setne %al;" +"pop %rdx;" +"pop %rdi;" +FRAME_END +"ret;" +".popsection"); + +#endif + /* * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. */
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org> To: Waiman Long <longman@redhat.com> Cc: linux-arch@vger.kernel.org, "Juergen Gross" <jgross@suse.com>, "Jeremy Fitzhardinge" <jeremy@goop.org>, x86@kernel.org, kvm@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>, "Boris Ostrovsky" <boris.ostrovsky@oracle.com>, "Pan Xinhui" <xinhui.pan@linux.vnet.ibm.com>, "Paolo Bonzini" <pbonzini@redhat.com>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, "Chris Wright" <chrisw@sous-sol.org>, "Ingo Molnar" <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, xen-devel@lists.xenproject.org, "Alok Kataria" <akataria@vmware.com>, "Thomas Gleixner" <tglx@linutronix.de> Subject: Re: [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function Date: Fri, 10 Feb 2017 17:19:28 +0100 [thread overview] Message-ID: <20170210161928.GI6515@twins.programming.kicks-ass.net> (raw) In-Reply-To: <1486741389-8513-1-git-send-email-longman@redhat.com> On Fri, Feb 10, 2017 at 10:43:09AM -0500, Waiman Long wrote: > It was found when running fio sequential write test with a XFS ramdisk > on a VM running on a 2-socket x86-64 system, the %CPU times as reported > by perf were as follows: > > 69.75% 0.59% fio [k] down_write > 69.15% 0.01% fio [k] call_rwsem_down_write_failed > 67.12% 1.12% fio [k] rwsem_down_write_failed > 63.48% 52.77% fio [k] osq_lock > 9.46% 7.88% fio [k] __raw_callee_save___kvm_vcpu_is_preempt > 3.93% 3.93% fio [k] __kvm_vcpu_is_preempted > Thinking about this again, wouldn't something like the below also work? diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 099fcba4981d..6aa33702c15c 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -589,6 +589,7 @@ static void kvm_wait(u8 *ptr, u8 val) local_irq_restore(flags); } +#ifdef CONFIG_X86_32 __visible bool __kvm_vcpu_is_preempted(int cpu) { struct kvm_steal_time *src = &per_cpu(steal_time, cpu); @@ -597,6 +598,31 @@ __visible bool __kvm_vcpu_is_preempted(int cpu) } PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted); +#else + +extern bool __raw_callee_save___kvm_vcpu_is_preempted(int); + +asm( +".pushsection .text;" +".global __raw_callee_save___kvm_vcpu_is_preempted;" +".type __raw_callee_save___kvm_vcpu_is_preempted, @function;" +"__raw_callee_save___kvm_vcpu_is_preempted:" +FRAME_BEGIN +"push %rdi;" +"push %rdx;" +"movslq %edi, %rdi;" +"movq $steal_time+16, %rax;" +"movq __per_cpu_offset(,%rdi,8), %rdx;" +"cmpb $0, (%rdx,%rax);" +"setne %al;" +"pop %rdx;" +"pop %rdi;" +FRAME_END +"ret;" +".popsection"); + +#endif + /* * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. */
next prev parent reply other threads:[~2017-02-10 16:20 UTC|newest] Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-02-10 15:43 [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function Waiman Long 2017-02-10 15:43 ` Waiman Long 2017-02-10 16:19 ` Peter Zijlstra 2017-02-10 16:19 ` Peter Zijlstra [this message] 2017-02-10 16:19 ` Peter Zijlstra 2017-02-10 16:35 ` Waiman Long 2017-02-10 16:35 ` Waiman Long 2017-02-10 17:00 ` Waiman Long 2017-02-10 17:00 ` Waiman Long 2017-02-10 17:00 ` Waiman Long 2017-02-13 10:47 ` Peter Zijlstra 2017-02-13 10:47 ` Peter Zijlstra 2017-02-13 10:47 ` Peter Zijlstra 2017-02-13 10:53 ` Peter Zijlstra 2017-02-13 10:53 ` Peter Zijlstra 2017-02-13 10:53 ` Peter Zijlstra 2017-02-13 19:42 ` Waiman Long 2017-02-13 19:42 ` Waiman Long 2017-02-13 19:42 ` Waiman Long 2017-02-13 20:12 ` Waiman Long 2017-02-13 20:12 ` Waiman Long 2017-02-13 21:52 ` Peter Zijlstra 2017-02-13 21:52 ` Peter Zijlstra 2017-02-13 21:52 ` Peter Zijlstra 2017-02-13 22:00 ` hpa 2017-02-13 22:00 ` hpa 2017-02-13 22:00 ` hpa 2017-02-13 22:07 ` hpa 2017-02-13 22:07 ` hpa 2017-02-13 22:07 ` hpa 2017-02-13 22:34 ` Waiman Long 2017-02-13 22:34 ` Waiman Long 2017-02-13 22:34 ` Waiman Long 2017-02-13 22:36 ` hpa 2017-02-13 22:36 ` hpa 2017-02-13 22:36 ` hpa 2017-02-14 9:39 ` Peter Zijlstra 2017-02-14 9:39 ` Peter Zijlstra 2017-02-14 9:39 ` Peter Zijlstra 2017-02-14 14:46 ` Waiman Long 2017-02-14 14:46 ` Waiman Long 2017-02-14 14:46 ` Waiman Long 2017-02-14 16:03 ` Peter Zijlstra 2017-02-14 16:03 ` Peter Zijlstra 2017-02-14 16:03 ` Peter Zijlstra 2017-02-14 16:18 ` [Xen-devel] " Andrew Cooper 2017-02-14 16:18 ` Andrew Cooper 2017-02-14 16:18 ` [Xen-devel] " Andrew Cooper 2017-02-13 20:12 ` Waiman Long 2017-02-13 20:06 ` hpa 2017-02-13 20:06 ` hpa 2017-02-13 21:57 ` Peter Zijlstra 2017-02-13 21:57 ` Peter Zijlstra 2017-02-13 21:57 ` Peter Zijlstra 2017-02-13 22:24 ` Waiman Long 2017-02-13 22:24 ` Waiman Long 2017-02-13 22:31 ` Peter Zijlstra 2017-02-13 22:31 ` Peter Zijlstra 2017-02-13 22:31 ` Peter Zijlstra 2017-02-13 22:24 ` Waiman Long 2017-02-13 20:06 ` hpa 2017-02-13 19:41 ` Waiman Long 2017-02-13 19:41 ` Waiman Long 2017-02-13 19:41 ` Waiman Long 2017-02-10 16:35 ` Waiman Long 2017-02-10 16:22 ` Paolo Bonzini 2017-02-10 16:22 ` Paolo Bonzini 2017-02-10 16:22 ` Paolo Bonzini -- strict thread matches above, loose matches on Subject: below -- 2017-02-10 15:43 Waiman Long
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