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

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

> 
> Thanks in Advance!!!
> 
> Thanks and Regards,
> Vinoth Natarajan.
> 
[...]

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