Messages in this thread | | | Date | Thu, 12 Apr 2018 10:05:13 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf record: Remove unnecessary warning for missing sysfs entry |
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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 <tmricht@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
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