linux-kernel - Re: [PATCH v11 2/2] lib/test_bitmap: add tests for bitmap

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Message-ID: <093114e8-b02f-4df0-a0d4-8e9f86e2259d@intel.com>
Date:   Thu, 9 Nov 2023 12:49:55 +0100
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Alexander Potapenko <glider@...gle.com>
CC:     <catalin.marinas@....com>, <will@...nel.org>, <pcc@...gle.com>,
        <andreyknvl@...il.com>, <andriy.shevchenko@...ux.intel.com>,
        <linux@...musvillemoes.dk>, <yury.norov@...il.com>,
        <alexandru.elisei@....com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <eugenis@...gle.com>,
        <syednwaris@...il.com>, <william.gray@...aro.org>
Subject: Re: [PATCH v11 2/2] lib/test_bitmap: add tests for
 bitmap_{read,write}()

From: Alexander Potapenko <glider@...gle.com>
Date: Mon, 30 Oct 2023 16:32:10 +0100

> Add basic tests ensuring that values can be added at arbitrary positions
> of the bitmap, including those spanning into the adjacent unsigned
> longs.
> 
> Two new performance tests, test_bitmap_read_perf() and
> test_bitmap_write_perf(), can be used to assess future performance
> improvements of bitmap_read() and bitmap_write():
> 
> [    0.431119][    T1] test_bitmap: Time spent in test_bitmap_read_perf:	615253
> [    0.433197][    T1] test_bitmap: Time spent in test_bitmap_write_perf:	916313
> 
> (numbers from a Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz machine running
> QEMU).
> 
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

[...]

> +static bool __init
> +__check_eq_ulong(const char *srcfile, unsigned int line,
> +		 const unsigned long exp_ulong, unsigned long x)
> +{
> +	if (exp_ulong != x) {
> +		pr_err("[%s:%u] expected %lu, got %lu\n",
> +			srcfile, line, exp_ulong, x);
> +		return false;
> +	}
> +	return true;
> +}

Could we maybe rather extend __check_eq_uint to take ulongs? Doesn't
seem like they differ a lot.

>  
>  static bool __init
>  __check_eq_bitmap(const char *srcfile, unsigned int line,

[...]

> +static void __init test_bitmap_read_perf(void)
> +{
> +	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
> +	unsigned int cnt, nbits, i;
> +	unsigned long val;
> +	ktime_t time;
> +
> +	bitmap_fill(bitmap, TEST_BIT_LEN);
> +	time = ktime_get();
> +	for (cnt = 0; cnt < 5; cnt++) {
> +		for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
> +			for (i = 0; i < TEST_BIT_LEN; i++) {
> +				if (i + nbits > TEST_BIT_LEN)
> +					break;
> +				/*
> +				 * Prevent the compiler from optimizing away the
> +				 * bitmap_read() by using its value.
> +				 */
> +				WRITE_ONCE(val, bitmap_read(bitmap, i, nbits));
> +			}
> +		}
> +	}
> +	time = ktime_get() - time;
> +	pr_err("Time spent in %s:\t%llu\n", __func__, time);

pr_err() is for printing errors and is shown in red by some log readers.
Maybe use pr_info() or pr_notice()? Definitely not an error or even warning.

> +}
> +
> +static void __init test_bitmap_write_perf(void)
> +{
> +	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
> +	unsigned int cnt, nbits, i;
> +	unsigned long val = 0xfeedface;
> +	ktime_t time;
> +
> +	bitmap_zero(bitmap, TEST_BIT_LEN);
> +	time = ktime_get();
> +	for (cnt = 0; cnt < 5; cnt++) {
> +		for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
> +			for (i = 0; i < TEST_BIT_LEN; i++) {
> +				if (i + nbits > TEST_BIT_LEN)
> +					break;
> +				bitmap_write(bitmap, val, i, nbits);
> +			}
> +		}
> +	}
> +	time = ktime_get() - time;
> +	pr_err("Time spent in %s:\t%llu\n", __func__, time);

(same)

> +}
> +
> +#undef TEST_BIT_LEN
> +
>  static void __init selftest(void)
>  {
>  	test_zero_clear();
> @@ -1237,6 +1411,9 @@ static void __init selftest(void)
>  	test_bitmap_cut();
>  	test_bitmap_print_buf();
>  	test_bitmap_const_eval();
> +	test_bitmap_read_write();
> +	test_bitmap_read_perf();
> +	test_bitmap_write_perf();
>  
>  	test_find_nth_bit();
>  	test_for_each_set_bit();

Thanks,
Olek