On 06/23/2011 06:11 PM, Frederic Weisbecker wrote:

On Thu, Jun 23, 2011 at 02:02:15PM -0600, David Ahern wrote:

quoted

On 06/23/2011 01:39 PM, Arun Sharma wrote:

quoted

On 6/23/11 7:22 AM, David Ahern wrote:

quoted

I have not seen issues like this using newer perf userspace against
older kernels. For example, my laptop was running Fedora 14 (2.6.35) and
now Fedora 15 (2.6.38.8) and I typically use latest perf builds (e.g.,
testing patches).

I narrowed it down to PERF_SAMPLE_RAW:

perf record -ag -- sleep 1

is fine, but:

perf record -agR -- sleep 1

fails for me most of the time. The reason I needed to use the -R in the
first place is that "perf script" fails on older kernels with:

Samples do not contain timestamps.

With the newer perf, I don't get errors, but the timestamp field is
invalid. So I need to use the -R flag to get valid timestamps +
stacktraces out of "perf script".

That should have been fixed.

And -T on record gets the timestamps.

David

Right, it would be nice to suggest that from perf script when timestamps
are not recorded.

Timestamps are enabled by default, but that output option is removed if
the samples do not have timestamps. That message is generated if the
user requests timestamps (-f time) in the perf-script output and the
samples do not have timestamps, but Arun did not request that. Arun's
mileage with perf-3.0 definitely varies from what I've seen.

David