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Date: Thu, 23 Jun 2011 23:14:19 -0600 From: David Ahern <dsahern@...il.com> To: Frederic Weisbecker <fweisbec@...il.com> CC: Arun Sharma <asharma@...com>, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: Using a new perf tool against an older kernel On 06/23/2011 06:11 PM, Frederic Weisbecker wrote: > On Thu, Jun 23, 2011 at 02:02:15PM -0600, David Ahern wrote: >> >> >> On 06/23/2011 01:39 PM, Arun Sharma wrote: >>> On 6/23/11 7:22 AM, David Ahern wrote: >>> >>>> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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