Re: [PATCH 2/2] xor/kunit: add a benchmark

[Eric Biggers]

On Wed, Jun 17, 2026 at 07:44:04AM +0200, Christoph Hellwig wrote:
> diff --git a/lib/raid/xor/tests/xor_kunit.c b/lib/raid/xor/tests/xor_kunit.c
> index 659ae3edbc25..5939b78b3944 100644
> --- a/lib/raid/xor/tests/xor_kunit.c
> +++ b/lib/raid/xor/tests/xor_kunit.c
> @@ -125,8 +125,71 @@ static void xor_test(struct kunit *test)
>  	}
>  }
>  
> +#ifdef CONFIG_XOR_BENCHMARK
> +static void xor_benchmark(struct kunit *test)

The #ifdef can be avoided using kunit_skip(), as the crypto and CRC
tests do:

    if (!IS_ENABLED(CONFIG_XOR_BENCHMARK))
            kunit_skip(test, "not enabled");

> +		for (j = 0; j < ARRAY_SIZE(len_to_test); j++) {
> +			unsigned int len = len_to_test[j];
> +			const unsigned long num_iters = 1000;
> +
> +			KUNIT_ASSERT_GT(test, len, 0);
> +			KUNIT_ASSERT_LE(test, len, XOR_KUNIT_MAX_BYTES);
> +
> +			preempt_disable();
> +			t = ktime_get();
> +			for (l = 0; l < num_iters; l++)
> +				xor_gen(test_dest, test_buffers, nr, len);
> +			t = ktime_get_ns() - t;
> +			preempt_enable();

First one should be ktime_get_ns(), not ktime_get().

> +
> +			speed[j] = div_u64((u64)len * num_iters * nr, t);
> +		}
> +
> +		static_assert(ARRAY_SIZE(len_to_test) == 2);
> +		kunit_info(test, "%3u disks:\t%5llu  GB/s\t%5llu  GB/s\n",
> +				nr, speed[0], speed[1]);

As mentioned in the other thread, this measures the speed at which the
source data is consumed, which differs from the code in
lib/raid/xor/xor-core.c that measures the speed at which the destination
data is produced.  Probably best to make them consistent.

- Eric