linux-kernel - Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

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Date:   Tue, 15 Mar 2022 12:19:36 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        kim.phillips@....com, acme@...hat.com, jolsa@...hat.com,
        songliubraving@...com, Stephane Eranian <eranian@...gle.com>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

Arnaldo,

On 09-Feb-22 9:17 PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Feb 08, 2022 at 01:16:35PM -0800, Stephane Eranian escreveu:
>> From: Kim Phillips <kim.phillips@....com>
>>
>> improve the error message returned on failed perf_event_open() on AMD when
>> using IBS.
>>
>> Output of executing 'perf record -e ibs_op// true' BEFORE this patch:
>>
>> The sys_perf_event_open() syscall returned with 22 (Invalid argument)for event (ibs_op//u).
>> /bin/dmesg | grep -i perf may provide additional information.
> 
> Humm, here on a
> 
>   $ grep -m1 'model name' /proc/cpuinfo
>   model name	: AMD Ryzen 9 5950X 16-Core Processor
>   $ ls -la /sys/devices/ibs_op
>   total 0
>   drwxr-xr-x.  4 root root    0 Feb  9 07:12 .
>   drwxr-xr-x. 21 root root    0 Feb  9 07:12 ..
>   drwxr-xr-x.  2 root root    0 Feb  9 12:17 format
>   -rw-r--r--.  1 root root 4096 Feb  9 12:21 perf_event_mux_interval_ms
>   drwxr-xr-x.  2 root root    0 Feb  9 12:21 power
>   lrwxrwxrwx.  1 root root    0 Feb  9 07:12 subsystem -> ../../bus/event_source
>   -r--r--r--.  1 root root 4096 Feb  9 12:17 type
>   -rw-r--r--.  1 root root 4096 Feb  9 07:12 uevent
>   $ cat /sys/devices/ibs_op/type
>   9
>   $
> 
> Running without this patch:
> 
>   $ uname -a
>   Linux five 5.15.14-100.fc34.x86_64 #1 SMP Tue Jan 11 16:53:51 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
>   $
> 
>   $ cat /etc/redhat-release
>   Fedora release 34 (Thirty Four)
>   $
> 
>   $ perf record -e ibs_op// true
>   Error:
>   Invalid event (ibs_op//u) in per-thread mode, enable system wide with '-a'.
>   $
> 
> Trying with system wide:
> 
>   $ perf record -a -e ibs_op// true
>   Error:
>   The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (ibs_op//u).
>   /bin/dmesg | grep -i perf may provide additional information.
>   
>   $
> 
> So you're missing -a in all examples? Am I missing something?

AMD IBS does not support per-thread monitoring because it's configured
as uncore pmu (perf_invalid_context).

Thanks,
Ravi