Em Thu, Apr 12, 2018 at 01:47:23PM +0200, Thomas Richter escreveu:
> Using perf on 4.16.0 kernel on s390 shows warning
> failed: can't open node sysfs data
> each time I run command perf record ... for example:
>
> [root@s35lp76 perf]# ./perf record -e rB0000 -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> failed: can't open node sysfs data
> [ perf record: Captured and wrote 0.001 MB perf.data (4 samples) ]
> [root@s35lp76 perf]#
>
> BTW: I find this error message not very informative.
What an understatement :-)
> It turns out commit e2091cedd51bf ("perf tools: Add MEM_TOPOLOGY
> feature to perf data file") tries to open directory named
> /sys/devices/system/node/ which does not exist on s390.
>
> This is the call stack:
> __cmd_record
> +---> perf_session__write_header
> +---> perf_header__adds_write
> +---> do_write_feat
> +---> write_mem_topology
> +---> build_mem_topology
> prints warning
> The issue starts in do_write_feat() which unconditionally
> loops over all features and now includes HEADER_MEM_TOPOLOGY and calls
> write_mem_topology().
> Function record__init_features() at the beginning of __cmd_record()
> sets all features and then turns off some.
>
> Fix this by removed the warning, if the directory is not present
> memory node information is not available and won't be displayed.
Can't we instead improve the error message and turn this into a
pr_debug2? Isn't it a reasonable scenario that the user expects this
topology information to be present and then ends up without it?
Perhaps something like:
pr_debug2("%s: could't read %s, does this arch have topology
information?\n", __func__, path);
- Arnaldo
> Signed-off-by: Thomas Richter <tmri...@linux.ibm.com>
> ---
> tools/perf/util/header.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 121df1683c36..4a3bfc900a68 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1320,7 +1320,6 @@ static int build_mem_topology(struct memory_node
> *nodes, u64 size, u64 *cntp)
>
> dir = opendir(path);
> if (!dir) {
> - pr_warning("failed: can't open node sysfs data\n");
> return -1;
> }
>
> --
> 2.14.3
