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

From: Hemant Kumar <[email-masked]>
Date: Tue, 12 May 2015 21:34:52 +0530

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 <[email-masked]>
>>
>> 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 <[email-masked]>
>> Signed-off-by: Hemant Kumar <[email-masked]>
>> ---
>> 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