Re: [PATCH] Remove Powerpc OProfile events the kernel will reject

On Thu, 2015-11-26 at 17:52 -0600, 大平怜 wrote:
> Hi Carl,
> 
> 
> I am using the commit a58c3953a1c5f5fb00b873a5e22c878f9f4d5a2d, which
> was the latest before your patch was applied, in the git repository.
> My machine is bare-metal POWER8, running Linux 3.16.0:
> 
> 
> cpu : POWER8E (raw), altivec supported
> clock : 2061.000000MHz
> revision : 2.1 (pvr 004b 0201)
> 
> 
> $ uname -r
> 3.16.0-31-generic
> $ uname -v
> #41-Ubuntu SMP Tue Feb 10 21:05:50 UTC 2015
> $ uname -m
> ppc64le
> 
>         > > The event code for  PM_DATA_ALL_FROM_RL2L3_MOD is
>         0x62c046.  Bits 22:20
>         > > are 2. According to the note 1 in the patch the kernel
>         will reject any
>         > > event with non zero bits in 22:20.  Hence it was included.
>         I tried the
>         > > event on my Power 8 machine:
> 
> 
> The bits 22:20 of 0x62c046 are 6, aren't they?  By the way, in my
> understanding,
> any event with non zero bits in 22:20 will be rejected,
> only when unit >= 6 && unit <= 9.  The unit (bits 15:12) of 0x62c046
> is 0xc.
> Hence PM_DATA_ALL_FROM_RL2L3_MOD should not be rejected.
> 

OK, I checked any yes I agree this should be unit c.  The perf code
shouldn't be rejecting it if it is unit 0xc.  So there is something else
causing the event to be rejected.

> 
> 
> 
>         > > ocount -e PM_DATA_ALL_FROM_RL2L3_MOD ls
>         > > Cannot find event PM_DATA_ALL_FROM_RL2L3_MOD
>         > > Error retrieving info for event PM_DATA_ALL_FROM_RL2L3_MOD
>         > >
>         > > and it was rejected.
> 
> 
> If it was the kernel that rejected the event, the error message should
> have been something like this:
> 
> 
> $ ./ocount -e PM_L2_LD_MISS ls
> perf_event_open failed with Invalid argument
> Caught runtime error while setting up counters
> Internal Error.  Perf event setup failed.
> Error running ocount
> 
> 
> Your error message simply said there was no such event, like this:

So, I grepped the error messages "Cannot find event" and "Error
retrieving info for event", these are messages in the OProfile source
code.  Specifically, libpe_utils/op_pe_utils.cpp.  I have started
digging to see why the OProfile code is not finding the info.  My first
thought is there is something missing in the libpfm.  I haven't chased
that down.  I will try and see if I can track down why OProfile is
having an issue with the event.  It looks like there are a few others
that also have unit 0xc which I removed because they are not working.
When we figure out why this event is not working it should fix a few of
the other events as well.

                  Carl Love




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