[PATCH v10-mte 2/7] lib/test_bitmap: add tests for bitmap_{read,write}()
From: Alexander Potapenko
Date: Thu Dec 14 2023 - 06:07:00 EST
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@xxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
v10-mte:
- send this patch together with the "Implement MTE tag compression for
swapped pages"
Revisions v8-v12 of bitmap patches were reviewed separately from the
"Implement MTE tag compression for swapped pages" series
(https://lore.kernel.org/lkml/20231109151106.2385155-1-glider@xxxxxxxxxx/)
This patch was previously called
"lib/test_bitmap: add tests for bitmap_{set,get}_value()"
(https://lore.kernel.org/lkml/20230720173956.3674987-3-glider@xxxxxxxxxx/)
and
"lib/test_bitmap: add tests for bitmap_{set,get}_value_unaligned"
(https://lore.kernel.org/lkml/20230713125706.2884502-3-glider@xxxxxxxxxx/)
v12:
- as suggested by Alexander Lobakin, replace expect_eq_uint() with
expect_eq_ulong() and a cast
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 | 179 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 172 insertions(+), 7 deletions(-)
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 65f22c2578b06..46c0154680772 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -60,18 +60,17 @@ static const unsigned long exp3_1_0[] __initconst = {
};
static bool __init
-__check_eq_uint(const char *srcfile, unsigned int line,
- const unsigned int exp_uint, unsigned int x)
+__check_eq_ulong(const char *srcfile, unsigned int line,
+ const unsigned long exp_ulong, unsigned long x)
{
- if (exp_uint != x) {
- pr_err("[%s:%u] expected %u, got %u\n",
- srcfile, line, exp_uint, 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,
const unsigned long *exp_bmap, const unsigned long *bmap,
@@ -185,7 +184,8 @@ __check_eq_str(const char *srcfile, unsigned int line,
result; \
})
-#define expect_eq_uint(...) __expect_eq(uint, ##__VA_ARGS__)
+#define expect_eq_ulong(...) __expect_eq(ulong, ##__VA_ARGS__)
+#define expect_eq_uint(x, y) expect_eq_ulong((unsigned int)(x), (unsigned int)(y))
#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__)
@@ -1245,6 +1245,168 @@ 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();
@@ -1261,6 +1423,9 @@ 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();
--
2.43.0.472.g3155946c3a-goog