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

[Namhyung Kim]

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
>