perf trace: Provide a better explanation when mmap fails
authorArnaldo Carvalho de Melo <acme@redhat.com>
Thu, 11 Dec 2014 21:04:10 +0000 (18:04 -0300)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Thu, 11 Dec 2014 21:04:10 +0000 (18:04 -0300)
If we ask for a mmap lenght than the max configured via the relevant
sysctl, provide a better warning, instead of just expanding the EPERM
returned:

[acme@ssdandy ~]$ trace -m 256 -e nanosleep sleep 2
Error: Operation not permitted.
Hint: Check /proc/sys/kernel/perf_event_mlock_kb (516 kB) setting.
Hint: Tried using 1028 kB.
Hint: Try using a bigger -m/--mmap-pages value.

[acme@ssdandy ~]$ trace -m 128 -e nanosleep sleep 2
  2001.280 (2000.403 ms): nanosleep(rqtp: 0x7fff89a8a7f0) = 0
[acme@ssdandy ~]$

An upcoming patch will autotune the request for non-root users when -m
is not used.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-cdvxfz2gycetbkopm9sna1qp@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/builtin-trace.c

index 83a4835c8118c5d4fa45aa9f4010e6e4cf33e45d..327541e43c7ffaf7bcb2b20af02f90bb01d10e59 100644 (file)
@@ -2045,7 +2045,6 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
        unsigned long before;
        const bool forks = argc > 0;
        bool draining = false;
-       char sbuf[STRERR_BUFSIZE];
 
        trace->live = true;
 
@@ -2106,11 +2105,8 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
                goto out_error_open;
 
        err = perf_evlist__mmap(evlist, trace->opts.mmap_pages, false);
-       if (err < 0) {
-               fprintf(trace->output, "Couldn't mmap the events: %s\n",
-                       strerror_r(errno, sbuf, sizeof(sbuf)));
-               goto out_delete_evlist;
-       }
+       if (err < 0)
+               goto out_error_mmap;
 
        perf_evlist__enable(evlist);
 
@@ -2210,6 +2206,10 @@ out_error_tp:
        perf_evlist__strerror_tp(evlist, errno, errbuf, sizeof(errbuf));
        goto out_error;
 
+out_error_mmap:
+       perf_evlist__strerror_mmap(evlist, errno, errbuf, sizeof(errbuf));
+       goto out_error;
+
 out_error_open:
        perf_evlist__strerror_open(evlist, errno, errbuf, sizeof(errbuf));