Integrated: 7903722: JMH: Add xctrace-based perfnorm profiler for macOS

[Filipp Zhinkin]

On Sat, 4 May 2024 19:23:44 GMT, Filipp Zhinkin <fzhinkin at openjdk.org> wrote:

> Implementation of a perfnorm-alike profiler for macOS based on `xctrace` command line tool bundled with Xcode.
> 
> While the profiler is tested and seems to be working well, I consider it rather a preliminary version and open to a discussion on what and how it should measure.
> 
> Currently, the profiler only supports PMU counters sampling using `CPU Counters` instrument provided by the Instruments app / xctrace.
> Unfortunately, `CPU Counters` instrument has no default settings, unlike `Time Profiler` and `CPU Profiler` instruments used by the recently merged `xctraceasm` profiler.
> To use `CPU Counters`, a user has to create a template in the Instruments UI, select PMU events, save the template and then supply to `xctracenorm` as an argument.
> 
> This workflow not only prevents use of the profiler without preliminary manual configuration, but also tends to be annoying when it comes to measuring multiple events, as xctrace, unlike perf_events, does not support events multiplexing.
> 
> Thankfully, command-line-based configuration and default parameters could be emulated by building a custom Instruments package that imports data from `CPU Counters` and also supplies all required parameters.
> As you can guess, there's no way to get information about supported PMU events directly from xctrace, but it could be fetched from KPEP database files, stored is `/usr/share/kpep`.
> `xctracenorm` relies on that data to validate events specified by a user, if any, and also to print a help message that gives some insights into what could be sampled.
> 
> To sum up, there are a few things that were implemented to make `xctracenorm` profiler works:
> - CPU model deletion using `sysctl`;
> - KPEP file parsing to extract information about the PMU and all supported events;
> - selected performance events validation;
> - Instruments package building (generate XML, call a builder tool), packages are cached in `~/Library/Caches/org.openjdk.jmh`;
> - xctrace execution, resulting samples extraction, and aggregation;
> - samples postprocessing to calculate some additional metrics, like CPI and branch missprediction ratio.
> 
> Currently, if a user didn't specify any additional options, `xctracenorm` will sample instructions, cycles, branches and mispredicted branches events. 
> These were selected as events that should be supported in all hardware macOS runs on; only 4 events were selected for the same reason.
> 
> Profiling results look like this on M2-based MacBook:
> 
> java -jar ./benchmarks.jar -prof xctracenorm -f 1 JMHSamp...

This pull request has now been integrated.

Changeset: c2931c90
Author:    Filipp Zhinkin <fzhinkin at openjdk.org>
Committer: Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jmh/commit/c2931c90fd4079271b69a8a393dfe277634f3e52
Stats:     2515 lines in 12 files changed: 2495 ins; 0 del; 20 mod

7903722: JMH: Add xctrace-based perfnorm profiler for macOS

Reviewed-by: shade

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PR: https://git.openjdk.org/jmh/pull/131