Messages in this thread | | | Date | Thu, 17 Sep 2020 18:09:50 +0800 | From | Leo Yan <> | Subject | Re: [PATCHv3] perf kvm: add kvm-stat for arm64 |
| |
[ + Marc ]
On Thu, Sep 17, 2020 at 09:36:45AM +0900, Sergey Senozhatsky wrote:
[...]
> diff --git a/tools/perf/arch/arm64/util/kvm-stat.c b/tools/perf/arch/arm64/util/kvm-stat.c > new file mode 100644 > index 000000000000..32e58576f186 > --- /dev/null > +++ b/tools/perf/arch/arm64/util/kvm-stat.c > @@ -0,0 +1,86 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <errno.h> > +#include <memory.h> > +#include "../../util/evsel.h" > +#include "../../util/kvm-stat.h" > +#include "arm64_exception_types.h" > +#include "debug.h" > + > +define_exit_reasons_table(arm64_exit_reasons, kvm_arm_exception_type); > +define_exit_reasons_table(arm64_trap_exit_reasons, kvm_arm_exception_class); > + > +const char *kvm_trap_exit_reason = "esr_ec"; > +const char *vcpu_id_str = "id";
On Arm64, ftrace tracepoint "kvm_entry" doesn't contain the field "id" or field "vcpu_id", thus it always reads out the "id" is 0 and it is recorded into Perf's structure vcpu_event_record::vcpu_id and assigned to perf thread's private data "thread::private".
With current code, it will not mess up different vcpus' samples because now the samples are analyzed based on thread context, but since all threads' "vcpu_id" is zero, thus all samples are accounted for "vcpu_id=0" and cannot print out correct result with option "--vcpu":
$ perf kvm stat report --vcpu 4
Analyze events for all VMs, VCPU 4:
VM-EXIT Samples Samples% Time% Min Time Max Time Avg time
Total Samples:0, Total events handled time:0.00us.
This is an issue I observed, if we want to support option "--vcpu", seems we need to change ftrace event for "kvm_entry", but this will break ABI.
Essentially, this issue is caused by different archs using different format for ftrace event "kvm_entry", on x86 it contains feild "vcpu_id" but arm64 only just records "vcpu_pc".
@Marc, @Will, do you have any suggestion for this? Do you think it's feasible to add a new field "vcpu_id" into the tracepoint "kvm_entry" for Arm64's version?
Thanks, Leo
| |