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: <c1076dbd-de63-4a9e-a097-de0f64c74a95@linux.intel.com>
Date: Tue, 5 Aug 2025 08:57:01 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: 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 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.