From 11113334d1c5dd5355c86e531c29f1202a855c86 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 24 Oct 2012 18:05:51 +0200 Subject: vtime: Make vtime_account_system() irqsafe vtime_account_system() currently has only one caller with vtime_account() which is irq safe. Now we are going to call it from other places like kvm where irqs are not always disabled by the time we account the cputime. So let's make it irqsafe. The arch implementation part is now prefixed with "__". vtime_account_idle() arch implementation is prefixed accordingly to stay consistent. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Steven Rostedt Cc: Paul Gortmaker Cc: Tony Luck Cc: Fenghua Yu Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Martin Schwidefsky Cc: Heiko Carstens --- arch/s390/kernel/vtime.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/s390') diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index 790334427895..783e988c4e1e 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -140,6 +140,10 @@ void vtime_account(struct task_struct *tsk) } EXPORT_SYMBOL_GPL(vtime_account); +void __vtime_account_system(struct task_struct *tsk) +__attribute__((alias("vtime_account"))); +EXPORT_SYMBOL_GPL(__vtime_account_system); + void __kprobes vtime_stop_cpu(void) { struct s390_idle_data *idle = &__get_cpu_var(s390_idle); -- cgit v1.2.1 From b080935c8638e08134629d0a9ebdf35669bec14d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 5 Oct 2012 23:07:19 +0200 Subject: kvm: Directly account vtime to system on guest switch Switching to or from guest context is done on ioctl context. So by the time we call kvm_guest_enter() or kvm_guest_exit() we know we are not running the idle task. As a result, we can directly account the cputime using vtime_account_system(). There are two good reasons to do this: * We avoid some useless checks on guest switch. It optimizes a bit this fast path. * In the case of CONFIG_IRQ_TIME_ACCOUNTING, calling vtime_account() checks for irq time to account. This is pointless since we know we are not in an irq on guest switch. This is wasting cpu cycles for no good reason. vtime_account_system() OTOH is a no-op in this config option. * We can remove the irq disable/enable around kvm guest switch in s390. A further optimization may consist in introducing a vtime_account_guest() that directly calls account_guest_time(). Signed-off-by: Frederic Weisbecker Cc: Tony Luck Cc: Fenghua Yu Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Heiko Carstens Cc: Martin Schwidefsky Cc: Avi Kivity Cc: Marcelo Tosatti Cc: Joerg Roedel Cc: Alexander Graf Cc: Xiantao Zhang Cc: Christian Borntraeger Cc: Cornelia Huck Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Steven Rostedt Cc: Paul Gortmaker --- arch/s390/kvm/kvm-s390.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'arch/s390') diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index ecced9d18986..d91a95568002 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -608,9 +608,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu) kvm_s390_deliver_pending_interrupts(vcpu); vcpu->arch.sie_block->icptcode = 0; - local_irq_disable(); kvm_guest_enter(); - local_irq_enable(); VCPU_EVENT(vcpu, 6, "entering sie flags %x", atomic_read(&vcpu->arch.sie_block->cpuflags)); trace_kvm_s390_sie_enter(vcpu, @@ -629,9 +627,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu) VCPU_EVENT(vcpu, 6, "exit sie icptcode %d", vcpu->arch.sie_block->icptcode); trace_kvm_s390_sie_exit(vcpu, vcpu->arch.sie_block->icptcode); - local_irq_disable(); kvm_guest_exit(); - local_irq_enable(); memcpy(&vcpu->run->s.regs.gprs[14], &vcpu->arch.sie_block->gg14, 16); return rc; -- cgit v1.2.1