linux-kernel - Re: [PATCH v1 0/7] perf bench: Add qspinlock benchmark

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Message-ID: <aIr2ZdxmuBoCmDhw@google.com>
Date: Wed, 30 Jul 2025 21:51:49 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Yuzhuo Jing <yuzhuo@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Liang Kan <kan.liang@...ux.intel.com>, Yuzhuo Jing <yzj@...ch.edu>,
	Andrea Parri <parri.andrea@...il.com>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Charlie Jenkins <charlie@...osinc.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Barret Rhoden <brho@...gle.com>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Guo Ren <guoren@...nel.org>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 0/7] perf bench: Add qspinlock benchmark

Hello,

On Mon, Jul 28, 2025 at 07:26:33PM -0700, Yuzhuo Jing wrote:
> As an effort to improve the perf bench subcommand, this patch series
> adds benchmark for the kernel's queued spinlock implementation.
> 
> This series imports necessary kernel definitions such as atomics,
> introduces userspace per-cpu adapter, and imports the qspinlock
> implementation from the kernel tree to tools tree, with minimum
> adaptions.

But I'm curious how you handled difference in kernel vs. user space.
For example, normally kernel spinlocks imply no preemption but we cannot
guarantee that in userspace.

> 
> This subcommand enables convenient commands to investigate the
> performance of kernel lock implementations, such as using sampling:
> 
>     perf record -- ./perf bench sync qspinlock -t5
>     perf report

It'd be nice if you can share an example output of the change.

Thanks,
Namhyung

> 
> Yuzhuo Jing (7):
>   tools: Import cmpxchg and xchg functions
>   tools: Import smp_cond_load and atomic_cond_read
>   tools: Partial import of prefetch.h
>   tools: Implement userspace per-cpu
>   perf bench: Import qspinlock from kernel
>   perf bench: Add 'bench sync qspinlock' subcommand
>   perf bench sync: Add latency histogram functionality
> 
>  tools/arch/x86/include/asm/atomic.h           |  14 +
>  tools/arch/x86/include/asm/cmpxchg.h          | 113 +++++
>  tools/include/asm-generic/atomic-gcc.h        |  47 ++
>  tools/include/asm/barrier.h                   |  58 +++
>  tools/include/linux/atomic.h                  |  27 ++
>  tools/include/linux/compiler_types.h          |  30 ++
>  tools/include/linux/percpu-simulate.h         | 128 ++++++
>  tools/include/linux/prefetch.h                |  41 ++
>  tools/perf/bench/Build                        |   2 +
>  tools/perf/bench/bench.h                      |   1 +
>  .../perf/bench/include/mcs_spinlock-private.h | 115 +++++
>  tools/perf/bench/include/mcs_spinlock.h       |  19 +
>  tools/perf/bench/include/qspinlock-private.h  | 204 +++++++++
>  tools/perf/bench/include/qspinlock.h          | 153 +++++++
>  tools/perf/bench/include/qspinlock_types.h    |  98 +++++
>  tools/perf/bench/qspinlock.c                  | 411 ++++++++++++++++++
>  tools/perf/bench/sync.c                       | 329 ++++++++++++++
>  tools/perf/builtin-bench.c                    |   7 +
>  tools/perf/check-headers.sh                   |  32 ++
>  19 files changed, 1829 insertions(+)
>  create mode 100644 tools/include/linux/percpu-simulate.h
>  create mode 100644 tools/include/linux/prefetch.h
>  create mode 100644 tools/perf/bench/include/mcs_spinlock-private.h
>  create mode 100644 tools/perf/bench/include/mcs_spinlock.h
>  create mode 100644 tools/perf/bench/include/qspinlock-private.h
>  create mode 100644 tools/perf/bench/include/qspinlock.h
>  create mode 100644 tools/perf/bench/include/qspinlock_types.h
>  create mode 100644 tools/perf/bench/qspinlock.c
>  create mode 100644 tools/perf/bench/sync.c
> 
> -- 
> 2.50.1.487.gc89ff58d15-goog
>