9546531884
This patch removes a conditional jump from get_max_segment_size(). The x86-64 assembler code for this function without this patch is as follows: 206 return min_not_zero(mask - offset + 1, 0x0000000000000118 <+72>: not %rax 0x000000000000011b <+75>: and 0x8(%r10),%rax 0x000000000000011f <+79>: add $0x1,%rax 0x0000000000000123 <+83>: je 0x138 <bvec_split_segs+104> 0x0000000000000125 <+85>: cmp %rdx,%rax 0x0000000000000128 <+88>: mov %rdx,%r12 0x000000000000012b <+91>: cmovbe %rax,%r12 0x000000000000012f <+95>: test %rdx,%rdx 0x0000000000000132 <+98>: mov %eax,%edx 0x0000000000000134 <+100>: cmovne %r12d,%edx With this patch applied: 206 return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1; 0x000000000000003f <+63>: mov 0x28(%rdi),%ebp 0x0000000000000042 <+66>: not %rax 0x0000000000000045 <+69>: and 0x8(%rdi),%rax 0x0000000000000049 <+73>: sub $0x1,%rbp 0x000000000000004d <+77>: cmp %rbp,%rax 0x0000000000000050 <+80>: cmova %rbp,%rax 0x0000000000000054 <+84>: add $0x1,%eax Reviewed-by: Ming Lei <ming.lei@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Keith Busch <kbusch@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20221025191755.1711437-4-bvanassche@acm.org Reviewed-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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|---|---|---|
| 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 | ||
| .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 Restructured Text 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.