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@vger.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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