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

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Message-ID: <4E034C2C.30509@gmail.com>
Date:	Thu, 23 Jun 2011 08:22:36 -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 06/22/2011 03:39 PM, Arun Sharma wrote:
> 
> I ran into a few strange issues today using a new perf tool (3.0-rcX)
> against a 2.6.38 based kernel. Basic things seem to work:
> 
> # perf record -aR -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.443 MB perf.data (~19334 samples) ]
> 
> But:
> 
> # perf record -agR -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 1.558 MB perf.data (~68077 samples) ]
> Can't find id 9's machine
> Found 1 unknown events!
> 
> Is this an older tool processing a perf.data file generated by a more
> recent tool?
> 
> If that is not the case, consider reporting to
> linux-kernel@...r.kernel.org.
> 
> I couldn't tell if this is kernel/user space incompatibility or tighter
> error checking in the new perf tool. Before I start digging further,
> thought I'd ask if this combination is supported. The error message
> above doesn't ask me:
> 
> Are you using an old kernel?

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).

David

> 
>  -Arun
> 
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