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KVM: halt_polling: improve grow/shrink settings

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Right now halt_poll_ns can be change during runtime. The
grow and shrink factors can only be set during module load.
Lets fix several aspects of grow shrink:
- make grow/shrink changeable by root
- make all variables unsigned int
- read the variables once to prevent races

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Christian Borntraeger
2016-02-09 13:47:55 +01:00
committed by Paolo Bonzini
parent efef127c30
commit 6b6de68c63
2 changed files with 15 additions and 12 deletions
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18
virt/kvm/kvm_main.c
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@@ -72,11 +72,11 @@ module_param(halt_poll_ns, uint, S_IRUGO | S_IWUSR);
/* Default doubles per-vcpu halt_poll_ns. */
static unsigned int halt_poll_ns_grow = 2;
module_param(halt_poll_ns_grow, int, S_IRUGO);
module_param(halt_poll_ns_grow, uint, S_IRUGO | S_IWUSR);
/* Default resets per-vcpu halt_poll_ns . */
static unsigned int halt_poll_ns_shrink;
module_param(halt_poll_ns_shrink, int, S_IRUGO);
module_param(halt_poll_ns_shrink, uint, S_IRUGO | S_IWUSR);
/*
* Ordering of locks:
@@ -1943,14 +1943,15 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);
static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
{
int old, val;
unsigned int old, val, grow;
old = val = vcpu->halt_poll_ns;
grow = READ_ONCE(halt_poll_ns_grow);
/* 10us base */
if (val == 0 && halt_poll_ns_grow)
if (val == 0 && grow)
val = 10000;
else
val *= halt_poll_ns_grow;
val *= grow;
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
@@ -1958,13 +1959,14 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
{
int old, val;
unsigned int old, val, shrink;
old = val = vcpu->halt_poll_ns;
if (halt_poll_ns_shrink == 0)
shrink = READ_ONCE(halt_poll_ns_shrink);
if (shrink == 0)
val = 0;
else
val /= halt_poll_ns_shrink;
val /= shrink;
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);