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Commit 6b6de68c authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Paolo Bonzini
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KVM: halt_polling: improve grow/shrink settings 



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent efef127c

include/trace/events/kvm.h

+5 −4
Original line number Diff line number Diff line
@@ -359,14 +359,15 @@ TRACE_EVENT( 
#endif



TRACE_EVENT(kvm_halt_poll_ns,

	TP_PROTO(bool grow, unsigned int vcpu_id, int new, int old),

	TP_PROTO(bool grow, unsigned int vcpu_id, unsigned int new,

		 unsigned int old),

	TP_ARGS(grow, vcpu_id, new, old),



	TP_STRUCT__entry(

		__field(bool, grow)

		__field(unsigned int, vcpu_id)

		__field(int, new)

		__field(int, old)

		__field(unsigned int, new)

		__field(unsigned int, old)

	),



	TP_fast_assign(
@@ -376,7 +377,7 @@ TRACE_EVENT(kvm_halt_poll_ns, 
		__entry->old            = old;

	),



	TP_printk("vcpu %u: halt_poll_ns %d (%s %d)",

	TP_printk("vcpu %u: halt_poll_ns %u (%s %u)",

			__entry->vcpu_id,

			__entry->new,

			__entry->grow ? "grow" : "shrink",

virt/kvm/kvm_main.c

+10 −8
Original line number Diff line number Diff line
@@ -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);