perf userspace tools fixes for Ubuntu / linaro

Chase Douglas chase.douglas at canonical.com
Mon Aug 2 21:10:10 UTC 2010


On Mon, 2010-08-02 at 10:55 +0100, Dave Martin wrote:
> Hi there,
> 
> I worked on a few patches to the help the userspace perf tools do
> better at loading debug symbols -- this is particularly of interest on
> Ubuntu and Linaro where separated debug symbols in .ddebs are
> typically not loaded even when present.  Note that even with the
> patches, the contents of .ddebs are still not cached by perf along
> with the other profiled binaries, so you will still lose the symbols
> if you uninstall/upgrade your ddebs in the meantime.  This should get
> fixed in the future.
> 
> Due to mailserver issues, Arnaldo kindly helped merge these patches
> for me.  The patches are now merged to the linux-2.6-tip master
> branch.
> 
> 
> You can find details of the commits here:
> 
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/608775

Thanks for passing this along! I am interested in figuring out whether
we should backport the patches to Ubuntu Maverick.

I took a look at the first two patches that deal with the cwd issue.
Although it fixes a real bug, I'm not sure it's worthwhile to pull it
into the Ubuntu Maverick kernel because it's rather esoteric. For those
unaware, the bug is triggered by starting a perf record while inside a
directory along the path to the executable being recorded. For example:

/bin # perf record ls
/bin # pert report

The report will work but it won't find the debug symbols
in /usr/lib/debug/bin/ls. Moving to a different directory, like /tmp,
while recording is a work around.

Since the bug is likely never to be seen except when running perf inside
system directories (which doesn't seem like a good usage scenario), I'm
inclined to recommend not backporting this for Ubuntu.

However, I still don't fully understand the issue surrounding the
buildid cache bug fix. Can you provide more details on the issue this is
fixing? It may be something we want to consider for Maverick, but I need
more info to know what's going on.

Thanks,

-- Chase





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