Messages in this thread | | | Date | Sat, 23 Feb 2008 13:22:22 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: add the debugfs interface for the sysprof tool |
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* Pekka Enberg <penberg@cs.helsinki.fi> wrote:
> On Sat, Feb 23, 2008 at 10:11 AM, Andrew Morton > <akpm@linux-foundation.org> wrote: > > Seems a poor idea to me. Sure, oprofile is "hard to set up", but not if > > your distributor already did it for you. > > Have you tried sysprof? It's really nice to setup and use compared to > oprofile when profiling user-space.
yes, it's very nice and very usable - and that's all that matters really. It's almost a _duty_ of the mainstream kernel to include that trivial 200 lines of sysprof code, given how poor instrumentation support is on Linux.
As a comparison, here's a session of a newbie developer, meeting oprofile for the first time in his life (using a fresh package, oprofile-0.9.3-6.fc8):
----------------------> [ Newbie: WTF, no GUI tool? ] [ Narrator: we lose 90% of the developers at this point. ] [ Newbie is adventurous and has heard about opcontrol and tries it. ] # opcontrol
[ Newbie sees tons of output. User scratches head. After looking around, finds the following option listed: "-s/--start start data collection". That must be it! ]
# opcontrol -s No vmlinux file specified. You must specify the correct vmlinux file, e.g. opcontrol --vmlinux=/path/to/vmlinux If you do not have a vmlinux file, use opcontrol --no-vmlinux Enter opcontrol --help for full options
[ Newbie: WTF? Doesnt oprofile think that what I want to do is to profile ... the currently running kernel, wherever a kernel is and whatever a vmlinux might be?? ]
[ Narrator: At this point oprofile has confused about 99% of all user-space developers who have no freaking idea about what a vmlinux is. ]
[ Newbie user figures that --no-vmlinux might be the right option: ]
# opcontrol -s --no-vmlinux Option "--setup" not valid with "-s".
[ Newbie: WTF? what not valid? Why should i care? Damnit, i only want to profile stuff!!! ]
[ The newbie user eventually finds out that opcontrol help text is buggy and that -s does not mean --start, but --setup. ]
[ Narrator: we now have lost 99.99% of the first-time users. ]
[ Newbie, armed with this nontrivial piece of information: ]
# opcontrol --start --no-vmlinux Using default event: CPU_CLK_UNHALTED:100000:0:1:1 Using 2.6+ OProfile kernel interface. Using log file /var/lib/oprofile/samples/oprofiled.log Daemon started. Profiler running.
[ Newbie: wow, it's working! Lets start an infinite loop and lets try this opreport thing: ]
# opreport
CPU_CLK_UNHALT...| samples| %| ------------------ 160405 82.9309 loop
[ Newbie: hm, i see where the overhead is - but which function is calling it? ]
[ Newbie user wants to restart profiling and figures that opcontrol --reset will do that: ]
# opcontrol --reset Signalling daemon... done
[ GREAT! It even said "done". Now lets see our new profile: ]
# opreport opreport error: No sample file found: try running opcontrol --dump or specify a session containing sample files
[ Newbie: WTF???? ]
[ Narrator: we've now lost 99.99999% of the testers at this point. The reamining 10 kernel developers still using oprofile have written up all the commands to the back of their keyboards, for easy reference. ] <----------------------
We should hang our collective heads in shame. Oprofile is an utter joke in terms of usability. It had 5-10 years to get its stuff together and didnt.
200 lines of totally isolated sysprof code is the least thing we can do which we _must do_ to help our users.
Ingo
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