| Message ID | 20210420130825.15585-2-yoan.picchi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: add more event counters for kvm_stat | expand |
On Tue, 20 Apr 2021 14:08:23 +0100, Yoan Picchi <yoan.picchi@arm.com> wrote: > > This counter is meant to detect stage 2 page fault exits. This is meant to > measure how much those page fault influence the performance (by comparing > this number of exits to some other exit causes). > For now this counter is generic, but some more granularity is planned in > the next commits so that one know how much of the page fault are for memory > allocation, or for mmio for instance. The idea being that one using this > counter can get a better idea of what is trigerring those exits to try to > fix it. > > Signed-off-by: Yoan Picchi <yoan.picchi@arm.com> > --- > arch/arm64/include/asm/kvm_host.h | 1 + > arch/arm64/kvm/guest.c | 1 + > arch/arm64/kvm/mmu.c | 2 ++ > 3 files changed, 4 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 3d10e6527..02891ce94 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -561,6 +561,7 @@ struct kvm_vcpu_stat { > u64 wfi_exit_stat; > u64 mmio_exit_user; > u64 mmio_exit_kernel; > + u64 stage2_abort_exit; > u64 exits; > }; > > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c > index 9bbd30e62..82a4b6275 100644 > --- a/arch/arm64/kvm/guest.c > +++ b/arch/arm64/kvm/guest.c > @@ -38,6 +38,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { > VCPU_STAT("wfi_exit_stat", wfi_exit_stat), > VCPU_STAT("mmio_exit_user", mmio_exit_user), > VCPU_STAT("mmio_exit_kernel", mmio_exit_kernel), > + VCPU_STAT("stage2_abort_exit", stage2_abort_exit), > VCPU_STAT("exits", exits), > VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns), > VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns), > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 77cb2d28f..c3527ccf6 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -966,6 +966,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > fault_ipa = kvm_vcpu_get_fault_ipa(vcpu); > is_iabt = kvm_vcpu_trap_is_iabt(vcpu); > > + Please proofread your patches, and don't add spurious blank lines. > /* Synchronous External Abort? */ > if (kvm_vcpu_abt_issea(vcpu)) { > /* > @@ -980,6 +981,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) > > trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_esr(vcpu), > kvm_vcpu_get_hfar(vcpu), fault_ipa); > + vcpu->stat.stage2_abort_exit++; What is the benefit of this counter over, say, the tracepoint that is already in place? This tracepoint allows you to count these exits, and to actually find *why* you are exiting. If the purpose of this patch is to identify exit reasons, I'd say that the tracepoint is vastly superior in that respect. M.
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 3d10e6527..02891ce94 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -561,6 +561,7 @@ struct kvm_vcpu_stat { u64 wfi_exit_stat; u64 mmio_exit_user; u64 mmio_exit_kernel; + u64 stage2_abort_exit; u64 exits; }; diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 9bbd30e62..82a4b6275 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -38,6 +38,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { VCPU_STAT("wfi_exit_stat", wfi_exit_stat), VCPU_STAT("mmio_exit_user", mmio_exit_user), VCPU_STAT("mmio_exit_kernel", mmio_exit_kernel), + VCPU_STAT("stage2_abort_exit", stage2_abort_exit), VCPU_STAT("exits", exits), VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns), VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns), diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 77cb2d28f..c3527ccf6 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -966,6 +966,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) fault_ipa = kvm_vcpu_get_fault_ipa(vcpu); is_iabt = kvm_vcpu_trap_is_iabt(vcpu); + /* Synchronous External Abort? */ if (kvm_vcpu_abt_issea(vcpu)) { /* @@ -980,6 +981,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_esr(vcpu), kvm_vcpu_get_hfar(vcpu), fault_ipa); + vcpu->stat.stage2_abort_exit++; /* Check the stage-2 fault is trans. fault or write fault */ if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
This counter is meant to detect stage 2 page fault exits. This is meant to measure how much those page fault influence the performance (by comparing this number of exits to some other exit causes). For now this counter is generic, but some more granularity is planned in the next commits so that one know how much of the page fault are for memory allocation, or for mmio for instance. The idea being that one using this counter can get a better idea of what is trigerring those exits to try to fix it. Signed-off-by: Yoan Picchi <yoan.picchi@arm.com> --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/guest.c | 1 + arch/arm64/kvm/mmu.c | 2 ++ 3 files changed, 4 insertions(+)