linux-kernel - Re: Using a new perf tool against an older kernel

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Message-ID: <4E03968A.5010008@fb.com>
Date:	Thu, 23 Jun 2011 12:39:54 -0700
From:	Arun Sharma <asharma@...com>
To:	David Ahern <dsahern@...il.com>
CC:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Using a new perf tool against an older kernel

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".

  -Arun
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