linux-kernel - Re: [PATCH 5/5] perf tools kvm: Use "cycles" to sample guest for "kvm top" on Intel

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Message-ID: <5b4882dc-c90d-409b-8355-45d8b96df93f@linux.ibm.com>
Date: Tue, 5 Aug 2025 17:02:22 +0530
From: Aditya Bodkhe <adityab1@...ux.ibm.com>
To: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kevin Tian <kevin.tian@...el.com>, Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [PATCH 5/5] perf tools kvm: Use "cycles" to sample guest for "kvm
 top" on Intel


On 05/08/25 6:27 am, Mi, Dapeng wrote:
> On 8/5/2025 8:46 AM, Dapeng Mi wrote:
>> As same reason with previous patch, use "cyles" instead of "cycles:P"
>> event by default to sample guest for "perf kvm top" command on Intel
>> platforms.
>>
>> Reported-by: Kevin Tian <kevin.tian@...el.com>
>> Fixes: 634d36f82517 ("perf record: Just use "cycles:P" as the default event")
>> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
>> ---
>>   tools/perf/builtin-kvm.c | 30 +++++++++++++++++++++++++++++-
>>   1 file changed, 29 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
>> index 7e48d2437710..d72b40f3df12 100644
>> --- a/tools/perf/builtin-kvm.c
>> +++ b/tools/perf/builtin-kvm.c
>> @@ -2075,6 +2075,34 @@ __cmd_buildid_list(const char *file_name, int argc, const char **argv)
>>   	return ret;
>>   }
>>   
>> +static int __cmd_top(int argc, const char **argv)
>> +{
>> +	int i = 0, ret;
>> +	const char **rec_argv;
>> +
>> +	/*
>> +	 * kvm_add_default_arch_event() may add 2 extra options, so
>> +	 * allocate 2 more pointers in adavance.
>> +	 */
>> +	rec_argv = calloc(argc + 2 + 1, sizeof(char *));
>> +	if (!rec_argv)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < argc; i++)
>> +		rec_argv[i] = argv[i];
>> +
>> +	BUG_ON(i != argc);
>> +
>> +	ret = kvm_add_default_arch_event(&i, rec_argv);
>> +	if (ret)
>> +		return -EINVAL;
>> +
>> +	ret = cmd_top(i, rec_argv);
>> +	free(rec_argv);
>> +
>> +	return ret;
>> +}
>> +
>>   int cmd_kvm(int argc, const char **argv)
>>   {
>>   	const char *file_name = NULL;
>> @@ -2135,7 +2163,7 @@ int cmd_kvm(int argc, const char **argv)
>>   	else if (strlen(argv[0]) > 2 && strstarts("diff", argv[0]))
>>   		return cmd_diff(argc, argv);
>>   	else if (!strcmp(argv[0], "top"))
>> -		return cmd_top(argc, argv);
>> +		return __cmd_top(argc, argv);
>>   	else if (strlen(argv[0]) > 2 && strstarts("buildid-list", argv[0]))
>>   		return __cmd_buildid_list(file_name, argc, argv);
>>   #if defined(HAVE_KVM_STAT_SUPPORT) && defined(HAVE_LIBTRACEEVENT)
> This patch would impact powerpc platform as well. Base on the comments
> before kvm_add_default_arch_event() in
> tools/perf/arch/powerpc/util/kvm-stat.c, I suppose powerpc also needs this
> change, otherwise "perf kvm top" command can't sample guest records. But I
> have no any powerpc on my hand, so it's not tested on powerpc platform. Any
> test on powerpc is appreciated. Thanks.
I have powerpc systems . I will test can share the results .
>
>