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

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Date:	Thu, 23 Jun 2011 14:02:15 -0600
From:	David Ahern <dsahern@...il.com>
To:	Arun Sharma <asharma@...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 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

> 
>  -Arun
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