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Alexander Lobakin 97a532c3ac bitmap: introduce generic optimized bitmap_size() 
commit a37fbe666c upstream.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-08-29 17:33:14 +02:00
arch arm64: ACPI: NUMA: initialize all values of acpi_early_node_map to NUMA_NO_NODE 2024-08-29 17:33:13 +02:00
block block: fix deadlock between sd_remove & sd_release 2024-08-03 08:54:24 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-11 12:49:04 +02:00
Documentation mm/page_table_check: support userfault wr-protect entries 2024-08-19 06:04:29 +02:00
drivers bitmap: introduce generic optimized bitmap_size() 2024-08-29 17:33:14 +02:00
fs btrfs: rename bitmap_set_bits() -> btrfs_bitmap_set_bits() 2024-08-29 17:33:14 +02:00
include bitmap: introduce generic optimized bitmap_size() 2024-08-29 17:33:14 +02:00
init rust: SHADOW_CALL_STACK is incompatible with Rust 2024-08-11 12:47:24 +02:00
io_uring io_uring: fix io_match_task must_hold 2024-08-03 08:54:41 +02:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel bpf: Avoid kfree_rcu() under lock in bpf_lpm_trie. 2024-08-19 06:04:27 +02:00
lib bitmap: introduce generic optimized bitmap_size() 2024-08-29 17:33:14 +02:00
LICENSES
mm mm/debug_vm_pgtable: drop RANDOM_ORVALUE trick 2024-08-19 06:04:31 +02:00
net fou: remove warn in gue_gro_receive on unsupported protocol 2024-08-19 06:04:30 +02:00
rust rust: kernel: require Send for Module implementations 2024-05-17 12:01:56 +02:00
samples bpf: Replace bpf_lpm_trie_key 0-length array with flexible array 2024-08-19 06:04:27 +02:00
scripts kbuild: avoid build error when single DTB is turned into composite DTB 2024-08-03 08:54:36 +02:00
security selinux: revert our use of vma_is_initial_heap() 2024-08-29 17:33:11 +02:00
sound ALSA: hda/tas2781: fix wrong calibrated data order 2024-08-29 17:33:12 +02:00
tools bitmap: introduce generic optimized bitmap_size() 2024-08-29 17:33:14 +02:00
usr
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml
COPYING
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild
Kconfig
MAINTAINERS pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
Makefile Linux 6.6.47 2024-08-19 06:04:32 +02:00
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Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.