[PATCH 1/2] perf iostat: Use system-wide mode if the target cpu_list is unspecified

Like Xu
2021-09-27T08:11:36Z

From: Like Xu <likexu@tencent.com>

An iostate use case like "perf iostat 0000:16,0000:97 -- ls" should be
implemented to work in system-wide mode to ensure that the output from
print_header() is consistent with the user documentation perf-iostat.txt,
rather than incorrectly assuming that the kernel does not support it:

Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) \
for event (uncore_iio_0/event=0x83,umask=0x04,ch_mask=0xF,fc_mask=0x07/).
/bin/dmesg | grep -i perf may provide additional information.

This error is easily fixed by assigning system-wide mode by default
for IOSTAT_RUN only when the target cpu_list is unspecified.

Signed-off-by: Like Xu <likexu@tencent.com>
---
tools/perf/builtin-stat.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index f6e87b7be5fa..f0ecfda34ece 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -2408,6 +2408,8 @@ int cmd_stat(int argc, const char **argv)
goto out;
} else if (verbose)
iostat_list(evsel_list, &stat_config);
+ if (iostat_mode == IOSTAT_RUN && !target__has_cpu(&target))
+ target.system_wide = true;
}

if (add_default_attributes())
--
2.32.0