debian-packaging
/
linux
8
0
Fork 0
Code Releases Activity
linux/debian/patches/features/all/rt/KVM-use-simple-waitqueue-fo...

344 lines
9.9 KiB
Diff
Raw Blame History

From 73a22bd9fee012b115222b6b20b42fd8f581a089 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Wed, 8 Apr 2015 20:33:24 -0300
Subject: [PATCH 1/2] KVM: use simple waitqueue for vcpu->wq
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz
The problem:
On -RT, an emulated LAPIC timer instances has the following path:
1) hard interrupt
2) ksoftirqd is scheduled
3) ksoftirqd wakes up vcpu thread
4) vcpu thread is scheduled
This extra context switch introduces unnecessary latency in the
LAPIC path for a KVM guest.
The solution:
Allow waking up vcpu thread from hardirq context,
thus avoiding the need for ksoftirqd to be scheduled.
Normal waitqueues make use of spinlocks, which on -RT
are sleepable locks. Therefore, waking up a waitqueue
waiter involves locking a sleeping lock, which
is not allowed from hard interrupt context.
cyclictest command line:
# cyclictest -m -n -q -p99 -l 1000000 -h60 -D 1m
This patch reduces the average latency in my tests from 14us to 11us.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/arm/kvm/arm.c | 4 ++--
arch/arm/kvm/psci.c | 4 ++--
arch/powerpc/include/asm/kvm_host.h | 4 ++--
arch/powerpc/kvm/book3s_hv.c | 23 +++++++++++------------
arch/s390/include/asm/kvm_host.h | 2 +-
arch/s390/kvm/interrupt.c | 8 ++++----
arch/x86/kvm/lapic.c | 6 +++---
include/linux/kvm_host.h | 4 ++--
virt/kvm/async_pf.c | 4 ++--
virt/kvm/kvm_main.c | 16 ++++++++--------
10 files changed, 37 insertions(+), 38 deletions(-)
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -454,9 +454,9 @@ static int kvm_vcpu_first_run_init(struc
static void vcpu_pause(struct kvm_vcpu *vcpu)
{
- wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
+ struct swait_head *wq = kvm_arch_vcpu_wq(vcpu);
- wait_event_interruptible(*wq, !vcpu->arch.pause);
+ swait_event_interruptible(*wq, !vcpu->arch.pause);
}
static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -68,7 +68,7 @@ static unsigned long kvm_psci_vcpu_on(st
{
struct kvm *kvm = source_vcpu->kvm;
struct kvm_vcpu *vcpu = NULL;
- wait_queue_head_t *wq;
+ struct swait_head *wq;
unsigned long cpu_id;
unsigned long context_id;
phys_addr_t target_pc;
@@ -117,7 +117,7 @@ static unsigned long kvm_psci_vcpu_on(st
smp_mb(); /* Make sure the above is visible */
wq = kvm_arch_vcpu_wq(vcpu);
- wake_up_interruptible(wq);
+ swait_wake_interruptible(wq);
return PSCI_RET_SUCCESS;
}
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -283,7 +283,7 @@ struct kvmppc_vcore {
u8 in_guest;
struct list_head runnable_threads;
spinlock_t lock;
- wait_queue_head_t wq;
+ struct swait_head wq;
spinlock_t stoltb_lock; /* protects stolen_tb and preempt_tb */
u64 stolen_tb;
u64 preempt_tb;
@@ -607,7 +607,7 @@ struct kvm_vcpu_arch {
u8 prodded;
u32 last_inst;
- wait_queue_head_t *wqp;
+ struct swait_head *wqp;
struct kvmppc_vcore *vcore;
int ret;
int trap;
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -87,11 +87,11 @@ static void kvmppc_fast_vcpu_kick_hv(str
{
int me;
int cpu = vcpu->cpu;
- wait_queue_head_t *wqp;
+ struct swait_head *wqp;
wqp = kvm_arch_vcpu_wq(vcpu);
- if (waitqueue_active(wqp)) {
- wake_up_interruptible(wqp);
+ if (swaitqueue_active(wqp)) {
+ swait_wake_interruptible(wqp);
++vcpu->stat.halt_wakeup;
}
@@ -666,8 +666,8 @@ int kvmppc_pseries_do_hcall(struct kvm_v
tvcpu->arch.prodded = 1;
smp_mb();
if (vcpu->arch.ceded) {
- if (waitqueue_active(&vcpu->wq)) {
- wake_up_interruptible(&vcpu->wq);
+ if (swaitqueue_active(&vcpu->wq)) {
+ swait_wake_interruptible(&vcpu->wq);
vcpu->stat.halt_wakeup++;
}
}
@@ -1394,7 +1394,7 @@ static struct kvmppc_vcore *kvmppc_vcore
INIT_LIST_HEAD(&vcore->runnable_threads);
spin_lock_init(&vcore->lock);
spin_lock_init(&vcore->stoltb_lock);
- init_waitqueue_head(&vcore->wq);
+ init_swait_head(&vcore->wq);
vcore->preempt_tb = TB_NIL;
vcore->lpcr = kvm->arch.lpcr;
vcore->first_vcpuid = core * threads_per_subcore;
@@ -1875,10 +1875,9 @@ static void kvmppc_vcore_blocked(struct
{
struct kvm_vcpu *vcpu;
int do_sleep = 1;
+ DEFINE_SWAITER(wait);
- DEFINE_WAIT(wait);
-
- prepare_to_wait(&vc->wq, &wait, TASK_INTERRUPTIBLE);
+ swait_prepare(&vc->wq, &wait, TASK_INTERRUPTIBLE);
/*
* Check one last time for pending exceptions and ceded state after
@@ -1892,7 +1891,7 @@ static void kvmppc_vcore_blocked(struct
}
if (!do_sleep) {
- finish_wait(&vc->wq, &wait);
+ swait_finish(&vc->wq, &wait);
return;
}
@@ -1900,7 +1899,7 @@ static void kvmppc_vcore_blocked(struct
trace_kvmppc_vcore_blocked(vc, 0);
spin_unlock(&vc->lock);
schedule();
- finish_wait(&vc->wq, &wait);
+ swait_finish(&vc->wq, &wait);
spin_lock(&vc->lock);
vc->vcore_state = VCORE_INACTIVE;
trace_kvmppc_vcore_blocked(vc, 1);
@@ -1945,7 +1944,7 @@ static int kvmppc_run_vcpu(struct kvm_ru
kvmppc_start_thread(vcpu);
trace_kvm_guest_enter(vcpu);
} else if (vc->vcore_state == VCORE_SLEEPING) {
- wake_up(&vc->wq);
+ swait_wake(&vc->wq);
}
}
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -404,7 +404,7 @@ struct kvm_s390_irq_payload {
struct kvm_s390_local_interrupt {
spinlock_t lock;
struct kvm_s390_float_interrupt *float_int;
- wait_queue_head_t *wq;
+ struct swait_head *wq;
atomic_t *cpuflags;
DECLARE_BITMAP(sigp_emerg_pending, KVM_MAX_VCPUS);
struct kvm_s390_irq_payload irq;
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -836,13 +836,13 @@ int kvm_s390_handle_wait(struct kvm_vcpu
void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu)
{
- if (waitqueue_active(&vcpu->wq)) {
+ if (swaitqueue_active(&vcpu->wq)) {
/*
* The vcpu gave up the cpu voluntarily, mark it as a good
* yield-candidate.
*/
vcpu->preempted = true;
- wake_up_interruptible(&vcpu->wq);
+ swait_wake_interruptible(&vcpu->wq);
vcpu->stat.halt_wakeup++;
}
}
@@ -963,7 +963,7 @@ int kvm_s390_inject_program_int(struct k
spin_lock(&li->lock);
irq.u.pgm.code = code;
__inject_prog(vcpu, &irq);
- BUG_ON(waitqueue_active(li->wq));
+ BUG_ON(swaitqueue_active(li->wq));
spin_unlock(&li->lock);
return 0;
}
@@ -982,7 +982,7 @@ int kvm_s390_inject_prog_irq(struct kvm_
spin_lock(&li->lock);
irq.u.pgm = *pgm_info;
rc = __inject_prog(vcpu, &irq);
- BUG_ON(waitqueue_active(li->wq));
+ BUG_ON(swaitqueue_active(li->wq));
spin_unlock(&li->lock);
return rc;
}
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1067,7 +1067,7 @@ static void update_divide_count(struct k
static void apic_timer_expired(struct kvm_lapic *apic)
{
struct kvm_vcpu *vcpu = apic->vcpu;
- wait_queue_head_t *q = &vcpu->wq;
+ struct swait_head *q = &vcpu->wq;
struct kvm_timer *ktimer = &apic->lapic_timer;
if (atomic_read(&apic->lapic_timer.pending))
@@ -1076,8 +1076,8 @@ static void apic_timer_expired(struct kv
atomic_inc(&apic->lapic_timer.pending);
kvm_set_pending_timer(vcpu);
- if (waitqueue_active(q))
- wake_up_interruptible(q);
+ if (swaitqueue_active(q))
+ swait_wake_interruptible(q);
if (apic_lvtt_tscdeadline(apic))
ktimer->expired_tscdeadline = ktimer->tscdeadline;
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -230,7 +230,7 @@ struct kvm_vcpu {
int fpu_active;
int guest_fpu_loaded, guest_xcr0_loaded;
- wait_queue_head_t wq;
+ struct swait_head wq;
struct pid *pid;
int sigset_active;
sigset_t sigset;
@@ -691,7 +691,7 @@ static inline bool kvm_arch_has_noncoher
}
#endif
-static inline wait_queue_head_t *kvm_arch_vcpu_wq(struct kvm_vcpu *vcpu)
+static inline struct swait_head *kvm_arch_vcpu_wq(struct kvm_vcpu *vcpu)
{
#ifdef __KVM_HAVE_ARCH_WQP
return vcpu->arch.wqp;
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -94,8 +94,8 @@ static void async_pf_execute(struct work
trace_kvm_async_pf_completed(addr, gva);
- if (waitqueue_active(&vcpu->wq))
- wake_up_interruptible(&vcpu->wq);
+ if (swaitqueue_active(&vcpu->wq))
+ swait_wake_interruptible(&vcpu->wq);
mmput(mm);
kvm_put_kvm(vcpu->kvm);
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -217,7 +217,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu,
vcpu->kvm = kvm;
vcpu->vcpu_id = id;
vcpu->pid = NULL;
- init_waitqueue_head(&vcpu->wq);
+ init_swait_head(&vcpu->wq);
kvm_async_pf_vcpu_init(vcpu);
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
@@ -1794,7 +1794,7 @@ static int kvm_vcpu_check_block(struct k
void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
ktime_t start, cur;
- DEFINE_WAIT(wait);
+ DEFINE_SWAITER(wait);
bool waited = false;
start = cur = ktime_get();
@@ -1814,7 +1814,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcp
}
for (;;) {
- prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
+ swait_prepare(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
if (kvm_vcpu_check_block(vcpu) < 0)
break;
@@ -1823,7 +1823,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcp
schedule();
}
- finish_wait(&vcpu->wq, &wait);
+ swait_finish(&vcpu->wq, &wait);
cur = ktime_get();
out:
@@ -1839,11 +1839,11 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu
{
int me;
int cpu = vcpu->cpu;
- wait_queue_head_t *wqp;
+ struct swait_head *wqp;
wqp = kvm_arch_vcpu_wq(vcpu);
- if (waitqueue_active(wqp)) {
- wake_up_interruptible(wqp);
+ if (swaitqueue_active(wqp)) {
+ swait_wake_interruptible(wqp);
++vcpu->stat.halt_wakeup;
}
@@ -1944,7 +1944,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *m
continue;
if (vcpu == me)
continue;
- if (waitqueue_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
+ if (swaitqueue_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
continue;
if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
continue;
View Git Blame Copy Permalink