Messages in this thread | | | Date | Wed, 9 Dec 2009 09:43:41 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH -tip 0/8] perf-probe updates |
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* Ingo Molnar <mingo@elte.hu> wrote:
> One hickup is that -d/--del does not appear to be working yet: > > # perf probe -l > probe:schedule (on schedule) > > # perf probe -d probe:schedule > Fatal: Failed to write event: Invalid argument
Ah, that was with an older kernel - a freshly booted kernel with delete-probe syntax worked fine.
There's another small hickup i had - when i typoed 'perf probe -', it gave me:
# perf probe - No dwarf info found in the vmlinux - please rebuild with CONFIG_DEBUG_INFO. An error occurred in debuginfo analysis. Try to use symbols. Fatal: Failed to write event: Invalid argument
Similar thing happens if i try to probe a non-existent symbol:
# perf probe test No dwarf info found in the vmlinux - please rebuild with CONFIG_DEBUG_INFO. An error occurred in debuginfo analysis. Try to use symbols. Fatal: Failed to write event: Invalid argument
I think we should print something more helpful, such as:
# perf probe test Fatal: Kernel symbol 'test' not found - probe not added.
the debuginfo printout is not helpful in this case - we should fall back to symbols silently, unless the nature of the error indicates that we fail _because_ there's no debuginfo.
Here the failure was because the symbol does not exist.
There's similar problems in most other failure cases. Trying to remove a non-existent probe gives:
# perf probe -d test Warning: event "probe:test" is not found.
It should say something like:
# perf probe -d test Info: event "probe:test" does not exist, could not remove it.
Also, it's possible to add multiple probes to the same function, using 'perf probe schedule' + 'perf probe schedule', etc. While in general it makes sense to allow it, by default we should refuse the second, identical probe on the symbol - and add a -f/--force option to force duplicate probes. I.e. the second probe should print:
# perf probe schedule Info: event "probe:schedule" already exists. (Use -f to force a duplicate.)
etc. Please try out various sensible and also less sensible options of this tool and try to make it break - and see whether the behavior is intuitive and obvious to users - whether the messages are consistent, etc. etc.
Ingo
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