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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 Reviewed-by: Andy Shevchenko --- This patch was previously part of the "Implement MTE tag compression for swapped pages" series (https://lore.kernel.org/linux-arm-kernel/20231011172836.2579017-4-glider@google.com/T/) This patch was previously called "lib/test_bitmap: add tests for bitmap_{set,get}_value()" (https://lore.kernel.org/lkml/20230720173956.3674987-3-glider@google.com/) and "lib/test_bitmap: add tests for bitmap_{set,get}_value_unaligned" (https://lore.kernel.org/lkml/20230713125706.2884502-3-glider@google.com/) v9: - use WRITE_ONCE() to prevent optimizations in test_bitmap_read_perf() - update patch description v8: - as requested by Andy Shevchenko, add tests for reading/writing sizes > BITS_PER_LONG v7: - as requested by Yury Norov, add performance tests for bitmap_read() and bitmap_write() v6: - use bitmap API to initialize test bitmaps - as requested by Yury Norov, do not check the return value of bitmap_read(..., 0) - fix a compiler warning on 32-bit systems v5: - update patch title - address Yury Norov's comments: - rename the test cases - factor out test_bitmap_write_helper() to test writing over different background patterns; - add a test case copying a nontrivial value bit-by-bit; - drop volatile v4: - Address comments by Andy Shevchenko: added Reviewed-by: and a link to the previous discussion - Address comments by Yury Norov: - expand the bitmap to catch more corner cases - add code testing that bitmap_set_value() does not touch adjacent bits - add code testing the nbits==0 case - rename bitmap_{get,set}_value() to bitmap_{read,write}() v3: - switch to using bitmap_{set,get}_value() - change the expected bit pattern in test_set_get_value(), as the test was incorrectly assuming 0 is the LSB. --- lib/test_bitmap.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 177 insertions(+) diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c index f2ea9f30c7c5d..a4195c7376840 100644 --- a/lib/test_bitmap.c +++ b/lib/test_bitmap.c @@ -71,6 +71,17 @@ __check_eq_uint(const char *srcfile, unsigned int line, return true; } +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; +} static bool __init __check_eq_bitmap(const char *srcfile, unsigned int line, @@ -186,6 +197,7 @@ __check_eq_str(const char *srcfile, unsigned int line, }) #define expect_eq_uint(...) __expect_eq(uint, ##__VA_ARGS__) +#define expect_eq_ulong(...) __expect_eq(ulong, ##__VA_ARGS__) #define expect_eq_bitmap(...) __expect_eq(bitmap, ##__VA_ARGS__) #define expect_eq_pbl(...) __expect_eq(pbl, ##__VA_ARGS__) #define expect_eq_u32_array(...) __expect_eq(u32_array, ##__VA_ARGS__) @@ -1222,6 +1234,168 @@ static void __init test_bitmap_const_eval(void) BUILD_BUG_ON(~var != ~BIT(25)); } +/* + * Test bitmap should be big enough to include the cases when start is not in + * the first word, and start+nbits lands in the following word. + */ +#define TEST_BIT_LEN (1000) + +/* + * Helper function to test bitmap_write() overwriting the chosen byte pattern. + */ +static void __init test_bitmap_write_helper(const char *pattern) +{ + DECLARE_BITMAP(bitmap, TEST_BIT_LEN); + DECLARE_BITMAP(exp_bitmap, TEST_BIT_LEN); + DECLARE_BITMAP(pat_bitmap, TEST_BIT_LEN); + unsigned long w, r, bit; + int i, n, nbits; + + /* + * Only parse the pattern once and store the result in the intermediate + * bitmap. + */ + bitmap_parselist(pattern, pat_bitmap, TEST_BIT_LEN); + + /* + * Check that writing a single bit does not accidentally touch the + * adjacent bits. + */ + for (i = 0; i < TEST_BIT_LEN; i++) { + bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN); + bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN); + for (bit = 0; bit <= 1; bit++) { + bitmap_write(bitmap, bit, i, 1); + __assign_bit(i, exp_bitmap, bit); + expect_eq_bitmap(exp_bitmap, bitmap, + TEST_BIT_LEN); + } + } + + /* Ensure writing 0 bits does not change anything. */ + bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN); + bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN); + for (i = 0; i < TEST_BIT_LEN; i++) { + bitmap_write(bitmap, ~0UL, i, 0); + expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN); + } + + for (nbits = BITS_PER_LONG; nbits >= 1; nbits--) { + w = IS_ENABLED(CONFIG_64BIT) ? 0xdeadbeefdeadbeefUL + : 0xdeadbeefUL; + w >>= (BITS_PER_LONG - nbits); + for (i = 0; i <= TEST_BIT_LEN - nbits; i++) { + bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN); + bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN); + for (n = 0; n < nbits; n++) + __assign_bit(i + n, exp_bitmap, w & BIT(n)); + bitmap_write(bitmap, w, i, nbits); + expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN); + r = bitmap_read(bitmap, i, nbits); + expect_eq_ulong(r, w); + } + } +} + +static void __init test_bitmap_read_write(void) +{ + unsigned char *pattern[3] = {"", "all:1/2", "all"}; + DECLARE_BITMAP(bitmap, TEST_BIT_LEN); + unsigned long zero_bits = 0, bits_per_long = BITS_PER_LONG; + unsigned long val; + int i, pi; + + /* + * Reading/writing zero bits should not crash the kernel. + * READ_ONCE() prevents constant folding. + */ + bitmap_write(NULL, 0, 0, READ_ONCE(zero_bits)); + /* Return value of bitmap_read() is undefined here. */ + bitmap_read(NULL, 0, READ_ONCE(zero_bits)); + + /* + * Reading/writing more than BITS_PER_LONG bits should not crash the + * kernel. READ_ONCE() prevents constant folding. + */ + bitmap_write(NULL, 0, 0, READ_ONCE(bits_per_long) + 1); + /* Return value of bitmap_read() is undefined here. */ + bitmap_read(NULL, 0, READ_ONCE(bits_per_long) + 1); + + /* + * Ensure that bitmap_read() reads the same value that was previously + * written, and two consequent values are correctly merged. + * The resulting bit pattern is asymmetric to rule out possible issues + * with bit numeration order. + */ + for (i = 0; i < TEST_BIT_LEN - 7; i++) { + bitmap_zero(bitmap, TEST_BIT_LEN); + + bitmap_write(bitmap, 0b10101UL, i, 5); + val = bitmap_read(bitmap, i, 5); + expect_eq_ulong(0b10101UL, val); + + bitmap_write(bitmap, 0b101UL, i + 5, 3); + val = bitmap_read(bitmap, i + 5, 3); + expect_eq_ulong(0b101UL, val); + + val = bitmap_read(bitmap, i, 8); + expect_eq_ulong(0b10110101UL, val); + } + + for (pi = 0; pi < ARRAY_SIZE(pattern); pi++) + test_bitmap_write_helper(pattern[pi]); +} + +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); +} + +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); +} + +#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();