Re: Clarification on support of arm32 with kernel4.1 for oprofile 1.2.0

Hello William,

We are using ARMv7 Processor rev 3  hardware.

Thanks and Regards,
Vinoth Natarajan.

On Fri, Feb 16, 2018 at 8:32 AM, William Cohen <[email protected]> wrote:

> On 02/15/2018 11:07 AM, Michael Petlan wrote:
> > On Thu, 15 Feb 2018, Vinoth Natarajan wrote:
> >> Hello Michael,
> >> Thanks so much for the help.
> >>
> >> Cross compiled the hello.c with crosstools-arm-gcc-5.3-linux-
> 4.1-glibc-2.22
> >> and tested the executable on the target(arm32)
> >>
> >> Received the following error
> >> " ./hello
> >> Error opening leader 1"
> >>
> >
> > This points to the kernel perf subsystem. It cannot even open a simple
> event.
> > Not an OProfile's fault.
> >
> >>
> >> Following are the kernel configs related to PERF in target
> >>
> >>  cat /tmp/test |grep PERF
> >>
> >> CONFIG_HAVE_PERF_EVENTS=y
> >> CONFIG_PERF_USE_VMALLOC=y
> >> CONFIG_PERF_EVENTS=y
> >> # CONFIG_DEBUG_PERF_USE_VMALLOC is not set
> >> CONFIG_HAVE_PERF_REGS=y
> >> CONFIG_HAVE_PERF_USER_STACK_DUMP=y
> >> # CONFIG_PCIEASPM_PERFORMANCE is not set
> >> # CONFIG_HW_PERF_EVENTS is not set
> >
> > I believe you need CONFIG_HW_PERF_EVENTS=y on ARM.
> >
> >> # CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
> >> # CONFIG_CPU_FREQ_GOV_PERFORMANCE is not set
> >> # CONFIG_CLS_U32_PERF is not set
> >>
> >> Could you please share your feedback on this.
> >
> > You may also try to grep for perf in logs:
> >
> > # dmesg | grep -i -e perf -e pmu
> > [    1.375699] hw perfevents: enabled with armv8_pmuv3_0 PMU driver, 5
> counters available
> > [    1.403155] kvm [1]: GICV region size/alignment is unsafe, using
> trapping (reduced performance)
> > [    2.036285] xgene-pmu APMC0D5C:00: X-Gene PMU version 2
> >
> > ^^^ This is a log from the moment when my kernel identified and
> initialized
> > the PMU. You should see something like that too. Or better, after
> recompiling
> > your kernel with CONFIG_HW_PERF_EVENTS=y and booting, you should see
> something
> > like this (PMU-related logs). If there is some error in PMU init, you
> will see
> > it in the logs.
> >
> > I am afraid that without CONFIG_HW_PERF_EVENTS=y you cannot use the
> events.
> >
> > However, I don't guarantee that with CONFIG_HW_PERF_EVENTS=y it works.
> There
> > can be some firmware issues, ACPI issues, etc. I roughly remember some
> issue
> > when you'd need to boot with acpi=off to access the events, etc.
> >
> > Cheers,
> > Michael
>
> Hi,
>
> Another way that perf may fail to work is due to the device tree for the
> platform not describing the performance monitoring hardware:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=741325
>
> There also may be some ARM processors that don't have performance
> monitoring hardware or that kernel perf support doesn't recognize.
>
> What 32-bit ARM platform is the target?
>
> -Will
>
>

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