linux-kernel - Re: Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a'.

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Message-ID: <5acc07fe-d161-2977-29ab-1096afeefc4c@amd.com>
Date:   Tue, 11 Jul 2023 10:44:52 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Namhyung Kim <namhyung@...il.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Slade Watkins <srw@...dewatkins.net>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Kees Cook <keescook@...omium.org>, sandipan.das@....com,
        Bill Wendling <morbo@...gle.com>,
        clang-built-linux <llvm@...ts.linux.dev>,
        Yonghong Song <yhs@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: Invalid event (cycles:pp) in per-thread mode, enable system wide
 with '-a'.

On 11-Jul-23 2:52 AM, Nick Desaulniers wrote:
> On Sun, Jun 25, 2023 at 10:45 PM Ravi Bangoria <ravi.bangoria@....com> wrote:
>>
>> Hi Nick,
>>
>> On 23-Jun-23 9:53 PM, Nick Desaulniers wrote:
>>>>> On 12-Oct-22 3:02 AM, Nick Desaulniers wrote:
>>> Hi Ravi,
>>> Sorry, I'm not able to load a custom kernel image on my employer
>>> provided workstation, and I never got approval to expense hardware for
>>> testing this otherwise.
>>>
>>> Was there ever any update on this? I'm on 6.1.25 now and still cant run
>>> $ perf record -e cycles:pp --call-graph lbr <any command to profile>
>>
>> Per-process precise sampling on AMD platforms should work from 6.2-rc1
>> onward.
> 
> Ok, I can wait for my employer to ship 6.2 on our workstations.
> 
>> However, --call-graph=lbr is not supported on AMD (hw limitation).
> 
> On any AMD uarches? Is there an equivalent? LBR encoding is compact
> which makes working it much faster than DWARF or stack frame
> unwinding.

I understand that LBR call-stack is the fastest option but unfortunately
none of the current AMD uarch supports it.

Thanks,
Ravi