[PATCH net-next v5 12/21] bitmap: introduce generic optimized bitmap_size()
From: Alexander Lobakin <aleksander.lobakin@intel.com>
Date: 2024-02-01 12:24:33
Also in:
intel-wired-lan, linux-btrfs, linux-s390, lkml, ntfs3
Subsystem:
bitmap api, device-mapper (lvm), library code, s390 architecture, s390 common i/o layer, the rest · Maintainers:
Yury Norov, Alasdair Kergon, Mike Snitzer, Mikulas Patocka, Benjamin Marzinski, Andrew Morton, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Vineeth Vijayan, Peter Oberparleiter, Linus Torvalds
The number of times yet another open coded `BITS_TO_LONGS(nbits) * sizeof(long)` can be spotted is huge. Some generic helper is long overdue. Add one, bitmap_size(), but with one detail. BITS_TO_LONGS() uses DIV_ROUND_UP(). The latter works well when both divident and divisor are compile-time constants or when the divisor is not a pow-of-2. When it is however, the compilers sometimes tend to generate suboptimal code (GCC 13): 48 83 c0 3f add $0x3f,%rax 48 c1 e8 06 shr $0x6,%rax 48 8d 14 c5 00 00 00 00 lea 0x0(,%rax,8),%rdx %BITS_PER_LONG is always a pow-2 (either 32 or 64), but GCC still does full division of `nbits + 63` by it and then multiplication by 8. Instead of BITS_TO_LONGS(), use ALIGN() and then divide by 8. GCC: 8d 50 3f lea 0x3f(%rax),%edx c1 ea 03 shr $0x3,%edx 81 e2 f8 ff ff 1f and $0x1ffffff8,%edx Now it shifts `nbits + 63` by 3 positions (IOW performs fast division by 8) and then masks bits[2:0]. bloat-o-meter: add/remove: 0/0 grow/shrink: 20/133 up/down: 156/-773 (-617) Clang does it better and generates the same code before/after starting from -O1, except that with the ALIGN() approach it uses %edx and thus still saves some bytes: add/remove: 0/0 grow/shrink: 9/133 up/down: 18/-538 (-520) Note that we can't expand DIV_ROUND_UP() by adding a check and using this approach there, as it's used in array declarations where expressions are not allowed. Add this helper to tools/ as well. Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com> Acked-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> --- include/linux/bitmap.h | 8 +++++--- include/linux/cpumask.h | 2 +- tools/include/linux/bitmap.h | 7 ++++--- drivers/md/dm-clone-metadata.c | 5 ----- drivers/s390/cio/idset.c | 2 +- lib/math/prime_numbers.c | 2 -- 6 files changed, 11 insertions(+), 15 deletions(-)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 7ca0379be8c1..9a6a27a7f675 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h@@ -218,9 +218,11 @@ void bitmap_fold(unsigned long *dst, const unsigned long *orig, #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) +#define bitmap_size(nbits) (ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE) + static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); if (small_const_nbits(nbits)) *dst = 0;
@@ -230,7 +232,7 @@ static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) static inline void bitmap_fill(unsigned long *dst, unsigned int nbits) { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); if (small_const_nbits(nbits)) *dst = ~0UL;
@@ -241,7 +243,7 @@ static inline void bitmap_fill(unsigned long *dst, unsigned int nbits) static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, unsigned int nbits) { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); if (small_const_nbits(nbits)) *dst = *src;
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index cfb545841a2c..a2064c2a9441 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h@@ -839,7 +839,7 @@ static inline int cpulist_parse(const char *buf, struct cpumask *dstp) */ static inline unsigned int cpumask_size(void) { - return BITS_TO_LONGS(large_cpumask_bits) * sizeof(long); + return bitmap_size(large_cpumask_bits); } /*
diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index 8c6852dba04f..210c13b1b857 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h@@ -26,13 +26,14 @@ bool __bitmap_intersects(const unsigned long *bitmap1, #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) +#define bitmap_size(nbits) (ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE) + static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { if (small_const_nbits(nbits)) *dst = 0UL; else { - int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0, len); + memset(dst, 0, bitmap_size(nbits)); } }
@@ -84,7 +85,7 @@ static inline void bitmap_or(unsigned long *dst, const unsigned long *src1, */ static inline unsigned long *bitmap_zalloc(int nbits) { - return calloc(1, BITS_TO_LONGS(nbits) * sizeof(unsigned long)); + return calloc(1, bitmap_size(nbits)); } /*
diff --git a/drivers/md/dm-clone-metadata.c b/drivers/md/dm-clone-metadata.c
index c43d55672bce..47c1fa7aad8b 100644
--- a/drivers/md/dm-clone-metadata.c
+++ b/drivers/md/dm-clone-metadata.c@@ -465,11 +465,6 @@ static void __destroy_persistent_data_structures(struct dm_clone_metadata *cmd) /*---------------------------------------------------------------------------*/ -static size_t bitmap_size(unsigned long nr_bits) -{ - return BITS_TO_LONGS(nr_bits) * sizeof(long); -} - static int __dirty_map_init(struct dirty_map *dmap, unsigned long nr_words, unsigned long nr_regions) {
diff --git a/drivers/s390/cio/idset.c b/drivers/s390/cio/idset.c
index 0a1105a483bf..e5f28370a903 100644
--- a/drivers/s390/cio/idset.c
+++ b/drivers/s390/cio/idset.c@@ -18,7 +18,7 @@ struct idset { static inline unsigned long idset_bitmap_size(int num_ssid, int num_id) { - return BITS_TO_LONGS(num_ssid * num_id) * sizeof(unsigned long); + return bitmap_size(size_mul(num_ssid, num_id)); } static struct idset *idset_new(int num_ssid, int num_id)
diff --git a/lib/math/prime_numbers.c b/lib/math/prime_numbers.c
index d42cebf7407f..d3b64b10da1c 100644
--- a/lib/math/prime_numbers.c
+++ b/lib/math/prime_numbers.c@@ -6,8 +6,6 @@ #include <linux/prime_numbers.h> #include <linux/slab.h> -#define bitmap_size(nbits) (BITS_TO_LONGS(nbits) * sizeof(unsigned long)) - struct primes { struct rcu_head rcu; unsigned long last, sz;
--
2.43.0