Re: perf_events: zero time running and enabled, but non-zero count

[Corey Ashford]

Anyone had a chance to look at this test case yet?

Regards,

- Corey

Corey Ashford wrote:
> On 10/23/2009 01:57 PM, Ingo Molnar wrote:
> > * Corey Ashford<cjashfor@xxxxxxxxxxxxxxxxxx>  wrote:
> >
> > > > Btw., you might want to consider putting such testcases into a new
> > > > 'perf test' kind of utility (under tools/perf/builtin-test.c) that
> > > > does various tests such as reading a count and validating the
> > > > time-running/time-enabled values - so that we can see any bugs
> > > > directly.
> > >
> > > I'll see if I can put the test case in some sort of acceptable format
> > > like that.  Maybe we can use this one test case as the starting point
> > > for builtin-test.c.
> >
> > Yeah. Feel free to add just something minimal that solves your problem.
> > Others will add their testcases too i'm sure, once the basic command is
> > there.
> >
> >     Ingo
>
> Hi Ingo and Paul,
>
> I followed the directions Ingo provided for getting the -tip tree and 
> then attempted to build the perf tool that's in it and it doesn't build. 
>  I'm getting this error on a Power5 box:
>
> ../../lib/find_next_bit.c: In function ‘ext2_swabp’:
> ../../lib/find_next_bit.c:168: warning: passing argument 1 of 
> ‘__swab64p’ from incompatible pointer type
> make: *** [util/find_next_bit.o] Error 1
>
> I looked at the code and it looks ok to me.  There's a cast from an 
> "unsigned long *" to a "unsigned long long *", but those types should be 
> of the same size (in -m64 mode), so I don't know why this is failing.
>
> Some good news is that I have created a simple test case which 
> demonstrates the bug, but I haven't formulated it in the builtin-test.c 
> format yet, since I have been able to build perf.
>
> If you toss the attached file into the perf source directory and compile 
> it as follows:
>
> gcc -m64 -o petb perf_events_time_bug.c -lrt
>
> it will show the error:
> % ./petb
> [0] = 1
> [1] = 0 <- time enabled
> [2] = 0 <- time running
> [3] = 4559d1f8
> [4] = 1
> test failed!
>
> perf_events_time_bug.c -lrt
>
> If you compile it with:
>
> gcc -DDO_DISABLE -m66 -o petb perf_events_time_bug.c -lrt
>
> This will disable the event before reading it and then you will get the 
> correct times.
>
> % ./petb
> [0] = 1
> [1] = 2a50c1c8 <- time enabled
> [2] = 2a50c1c8 <- time running
> [3] = 460dea97
> [4] = 2
> test passed!

--
Regards,

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@xxxxxxxxxx

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