linux-kernel - Re: perf/x86/intel: Collecting CPU-local performance counters from all cores in parallel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <87o9uj47n7.fsf@firstfloor.org>
Date:   Tue, 23 May 2017 13:53:32 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Michael Edwards <michael@...syr.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        linux-perf-users@...r.kernel.org
Subject: Re: perf/x86/intel: Collecting CPU-local performance counters from all cores in parallel

Michael Edwards <michael@...syr.com> writes:
>
> Am I going about this wrong?

It seems like a reasonable optimization, but it's likely a lot of work.

> Is there some better way to pursue the
> high-level goal of gathering PMC-based statistics frequently and
> efficiently from all cores, without breaking everything else that uses
> perf_events?

If you can drive the collection from a performance counter
(e.g. reference cycles) you could use leader sampling, and let the
PMIs log the values to the mmap'ed ring buffer. This should
be vastly more efficient than pulling everything. This works today,
however there are some scaling problems with many groups still.

perf record -F frequency -e '{cpu/ref-cycles/,<three other
events to collect>}:S,... more groups like this ... -a ...

-Andi