Re: [PATCH v3 1/2] perf/kvm: Port perf kvm to powerpc

[Hemant Kumar]

Hi Scott,

On 05/12/2015 03:38 AM, Scott Wood wrote:
> On Fri, 2015-05-08 at 06:37 +0530, Hemant Kumar wrote:
> > From: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> >
> > perf kvm can be used to analyze guest exit reasons. This support already
> > exists in x86. Hence, porting it to powerpc.
> >
> >   - To trace KVM events :
> >    perf kvm stat record
> >    If many guests are running, we can track for a specific guest by using
> >    --pid as in : perf kvm stat record --pid <pid>
> >
> >   - To see the results :
> >    perf kvm stat report
> >
> > The result shows the number of exits (from the guest context to
> > host/hypervisor context) grouped by their respective exit reasons with
> > their frequency.
> >
> > This patch makes use of the guest exit reasons available in
> > "trace_book3s.h". It records on two already available tracepoints :
> > "kvm_hv:kvm_guest_exit" and "kvm_hv:kvm_guest_enter".
> >
> > Note : This patch has a dependency on the patch "kvm/powerpc: Export
> > kvm exit reasons" which exports the KVM exit reasons through the uapi.
> >
> > Here is a sample o/p:
> >   # pgrep qemu
> > 19378
> > 60515
> >
> > 2 Guests are running on the host.
> >
> >   # perf kvm stat record -a
> > ^C[ perf record: Woken up 1 times to write data ]
> > [ perf record: Captured and wrote 4.153 MB perf.data.guest (39624 samples) ]
> >
> >   # perf kvm stat report -p 60515
> > Analyze events for pid(s) 60515, all VCPUs:
> >
> >         VM-EXIT    Samples  Samples%     Time%    Min Time         Max        Time         Avg time
> >
> > H_DATA_STORAGE       5006    35.30%     0.13%      1.94us     49.46us     12.37us ( +-   0.52% )
> > HV_DECREMENTER       4457    31.43%     0.02%      0.72us     16.14us      1.91us ( +-   0.96% )
> >         SYSCALL       2690    18.97%     0.10%      2.84us    528.24us     18.29us ( +-   3.75% )
> > RETURN_TO_HOST       1789    12.61%    99.76%      1.58us 672791.91us  27470.23us ( +-   3.00% )
> >        EXTERNAL        240     1.69%     0.00%        0.69us     10.67us      1.33us ( +-   5.34% )
> >
> > Total Samples:14182, Total events handled time:49264158.30us.
> >
> > Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Hemant Kumar <hemant@xxxxxxxxxxxxxxxxxx>
> > ---
> > Patch has a dependency on : https://patchwork.ozlabs.org/patch/469839/
> > which exports the exit reasons to perf through uapi.
> >
> > Changes:
> > - Original series split into two patchsets now : perf and powerpc
> >    side changes.
> >
> >   arch/powerpc/include/uapi/asm/kvm_perf.h | 15 +++++++++++++++
> >   tools/perf/arch/powerpc/Makefile         |  1 +
> >   tools/perf/arch/powerpc/util/Build       |  1 +
> >   tools/perf/arch/powerpc/util/kvm-stat.c  | 33 ++++++++++++++++++++++++++++++++
> >   4 files changed, 50 insertions(+)
> >   create mode 100644 arch/powerpc/include/uapi/asm/kvm_perf.h
> >   create mode 100644 tools/perf/arch/powerpc/util/kvm-stat.c
> >
> > diff --git a/arch/powerpc/include/uapi/asm/kvm_perf.h b/arch/powerpc/include/uapi/asm/kvm_perf.h
> > new file mode 100644
> > index 0000000..30fa670
> > --- /dev/null
> > +++ b/arch/powerpc/include/uapi/asm/kvm_perf.h
> > @@ -0,0 +1,15 @@
> > +#ifndef _ASM_POWERPC_KVM_PERF_H
> > +#define _ASM_POWERPC_KVM_PERF_H
> > +
> > +#include <asm/trace_book3s.h>
> > +#include <asm/kvm.h>
> > +
> > +#define DECODE_STR_LEN 20
> > +
> > +#define VCPU_ID "vcpu_id"
> > +
> > +#define KVM_ENTRY_TRACE "kvm_hv:kvm_guest_enter"
> > +#define KVM_EXIT_TRACE "kvm_hv:kvm_guest_exit"
> > +#define KVM_EXIT_REASON "trap"
> > +
> > +#endif /* _ASM_POWERPC_KVM_PERF_H */
> Please make sure that anything book3s-specific is named that way.

Are you suggesting to name it to something like _ASM_POWERPC_BOOK3S_PERF_H ?

> And shouldn't this be part of the arch/powerpc-side patchset?

It should. Thanks, will move this to arch/powerpc side patchset.

> > diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> > index 7fbca17..21322e0 100644
> > --- a/tools/perf/arch/powerpc/Makefile
> > +++ b/tools/perf/arch/powerpc/Makefile
> > @@ -1,3 +1,4 @@
> >   ifndef NO_DWARF
> >   PERF_HAVE_DWARF_REGS := 1
> >   endif
> > +HAVE_KVM_STAT_SUPPORT := 1
> Does this stuff fail gracefully if used on a PPC target that doesn't
> support this?

Yes, it does.

> -Scott
>
>
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--
Thanks,
Hemant Kumar

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