Commit 2305c82f authored Sep 13, 2012 by David Ahern Committed by Arnaldo Carvalho de Melo Oct 24, 2012

perf tools: Give user better message if precise is not supported



Platforms (e.g., VM's) without support for precise mode get a confusing
error message. e.g.,
$ perf record -e cycles:p -a -- sleep 1

  Error: sys_perf_event_open() syscall returned with 95 (Operation not
  supported).  /bin/dmesg may provide additional information.

  No hardware sampling interrupt available. No APIC? If so then you can
  boot the kernel with the "lapic" boot parameter to force-enable it.
  sleep: Terminated

which is not clear that precise mode might be the root problem. With this
patch:

$ perf record -e cycles:p -fo /tmp/perf.data -- sleep 1
  Error:
  'precise' request may not be supported. Try removing 'p' modifier
  sleep: Terminated

v2: softened message to 'may not be' supported per Robert's suggestion

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Link: http://lkml.kernel.org/r/1347569955-54626-4-git-send-email-dsahern@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 03f2f93a

tools/perf/builtin-record.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -317,6 +317,11 @@ try_again:
		perf_evsel__name(pos));
		rc = -err;
		goto out;
		} else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
		ui__error("\'precise\' request may not be supported. "
		"Try removing 'p' modifier\n");
		rc = -err;
		goto out;
		}

		printf("\n");

tools/perf/builtin-top.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -977,6 +977,10 @@ try_again:
		ui__error("Too many events are opened.\n"
		"Try again after reducing the number of events\n");
		goto out_err;
		} else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
		ui__error("\'precise\' request may not be supported. "
		"Try removing 'p' modifier\n");
		goto out_err;
		}

		ui__error("The sys_perf_event_open() syscall "

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