KVM: add halt_attempted_poll to VCPU stats

This new statistic can help diagnosing VCPUs that, for any reason,
trigger bad behavior of halt_poll_ns autotuning.

For example, say halt_poll_ns = 480000, and wakeups are spaced exactly
like 479us, 481us, 479us, 481us. Then KVM always fails polling and wastes
10+20+40+80+160+320+480 = 1110 microseconds out of every
479+481+479+481+479+481+479 = 3359 microseconds. The VCPU then
is consuming about 30% more CPU than it would use without
polling.  This would show as an abnormally high number of
attempted polling compared to the successful polls.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com<
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index dcba0fa..687ddeb 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -148,6 +148,7 @@ struct kvm_vm_stat {
 
 struct kvm_vcpu_stat {
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
 };
 

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 415938d..4865945 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -195,6 +195,7 @@ struct kvm_vm_stat {
 
 struct kvm_vcpu_stat {
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
 };
 

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index e8c8d9d..3a54dbc 100644 (file)
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -128,6 +128,7 @@ struct kvm_vcpu_stat {
        u32 msa_disabled_exits;
        u32 flush_dcache_exits;
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
 };
 

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index cd4c129..49ff3bf 100644 (file)
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -55,6 +55,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "msa_disabled", VCPU_STAT(msa_disabled_exits), KVM_STAT_VCPU },
        { "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU },
+       { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll), KVM_STAT_VCPU },
        { "halt_wakeup",  VCPU_STAT(halt_wakeup),        KVM_STAT_VCPU },
        {NULL}
 };

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 98eebbf..195886a 100644 (file)
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -108,6 +108,7 @@ struct kvm_vcpu_stat {
        u32 dec_exits;
        u32 ext_intr_exits;
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
        u32 dbell_exits;
        u32 gdbell_exits;

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index d75bf32..cf00916 100644 (file)
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -53,6 +53,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "ext_intr",    VCPU_STAT(ext_intr_exits) },
        { "queue_intr",  VCPU_STAT(queue_intr) },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll), },
+       { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll), },
        { "halt_wakeup", VCPU_STAT(halt_wakeup) },
        { "pf_storage",  VCPU_STAT(pf_storage) },
        { "sp_storage",  VCPU_STAT(sp_storage) },

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index ae458f0..fd58751 100644 (file)
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -63,6 +63,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "dec",        VCPU_STAT(dec_exits) },
        { "ext_intr",   VCPU_STAT(ext_intr_exits) },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
+       { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll) },
        { "halt_wakeup", VCPU_STAT(halt_wakeup) },
        { "doorbell", VCPU_STAT(dbell_exits) },
        { "guest doorbell", VCPU_STAT(gdbell_exits) },

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 3d012e0..6ce4a0b 100644 (file)
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -210,6 +210,7 @@ struct kvm_vcpu_stat {
        u32 exit_validity;
        u32 exit_instruction;
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
        u32 instruction_lctl;
        u32 instruction_lctlg;

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c91eb94..2f807ab 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -63,6 +63,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "exit_program_interruption", VCPU_STAT(exit_program_interruption) },
        { "exit_instr_and_program_int", VCPU_STAT(exit_instr_and_program) },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
+       { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll) },
        { "halt_wakeup", VCPU_STAT(halt_wakeup) },
        { "instruction_lctlg", VCPU_STAT(instruction_lctlg) },
        { "instruction_lctl", VCPU_STAT(instruction_lctl) },

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c12e845..349f80a 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -711,6 +711,7 @@ struct kvm_vcpu_stat {
        u32 nmi_window_exits;
        u32 halt_exits;
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
        u32 request_irq_exits;
        u32 irq_exits;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a60bdbc..6bbb0df 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -149,6 +149,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "nmi_window", VCPU_STAT(nmi_window_exits) },
        { "halt_exits", VCPU_STAT(halt_exits) },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
+       { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll) },
        { "halt_wakeup", VCPU_STAT(halt_wakeup) },
        { "hypercalls", VCPU_STAT(hypercalls) },
        { "request_irq", VCPU_STAT(request_irq_exits) },

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9af68db..04146a2 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2004,6 +2004,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
        if (vcpu->halt_poll_ns) {
                ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
 
+               ++vcpu->stat.halt_attempted_poll;
                do {
                        /*
                         * This sets KVM_REQ_UNHALT if an interrupt