mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
synced 2026-11-10 20:48:12 +00:00
No description
- C 96.8%
- Assembly 0.9%
- Rust 0.7%
- Shell 0.6%
- Python 0.5%
- Other 0.3%
6da1cab4f5
Replace `cpumask_any_and(a, b) >= nr_cpu_ids`
with the more readable `!cpumask_intersects(a, b)`.
Comparison between cpumask_any_and() and cpumask_intersects()
The cpumask_any_and() function expands using FIND_FIRST_BIT(),
resulting in a loop that iterates through each bit of the bitmask:
for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {
val = (FETCH);
if (val) {
sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);
break;
}
}
The cpumask_intersects() function expands using __bitmap_intersects(),
resulting in that the first loop iterates through each long word of the bitmask,
and the second through each bit within a long word:
unsigned int k, lim = bits/BITS_PER_LONG;
for (k = 0; k < lim; ++k)
if (bitmap1[k] & bitmap2[k])
return true;
if (bits % BITS_PER_LONG)
if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
return true;
Conclusion: cpumask_intersects() is at least as efficient as cpumask_any_and(),
if not more so, as it typically performs fewer loops and comparisons.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20240926092623.399577-2-costa.shul@redhat.com
|
History
|
|
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
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.