mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-22 18:41:06 +00:00
No description
04746ed80b
core.c has become rather large, move most scheduler syscall related functionality into a separate file, syscalls.c. This is about ~15% of core.c's raw linecount. Move the alloc_user_cpus_ptr(), __rt_effective_prio(), rt_effective_prio(), uclamp_none(), uclamp_se_set() and uclamp_bucket_id() inlines to kernel/sched/sched.h. Internally export the __sched_setscheduler(), __sched_setaffinity(), __setscheduler_prio(), set_load_weight(), enqueue_task(), dequeue_task(), check_class_changed(), splice_balance_callbacks() and balance_callbacks() methods to better facilitate this. Move the new file's build to sched_policy.c, because it fits there semantically, but also because it's the smallest of the 4 build units under an allmodconfig build: -rw-rw-r-- 1 mingo mingo 7.3M May 27 12:35 kernel/sched/core.i -rw-rw-r-- 1 mingo mingo 6.4M May 27 12:36 kernel/sched/build_utility.i -rw-rw-r-- 1 mingo mingo 6.3M May 27 12:36 kernel/sched/fair.i -rw-rw-r-- 1 mingo mingo 5.8M May 27 12:36 kernel/sched/build_policy.i This better balances build time for scheduler subsystem rebuilds. I build-tested this new file as a standalone syscalls.o file for a bit, to make sure all the encapsulations & abstractions are robust. Also update/add my copyright notices to these files. Build time measurements: # -Before/+After: kepler:~/tip> perf stat -e 'cycles,instructions,duration_time' --sync --repeat 5 --pre 'rm -f kernel/sched/*.o' m kernel/sched/built-in.a >/dev/null Performance counter stats for 'm kernel/sched/built-in.a' (5 runs): - 71,938,508,607 cycles ( +- 0.17% ) + 71,992,916,493 cycles ( +- 0.22% ) - 106,214,780,964 instructions # 1.48 insn per cycle ( +- 0.01% ) + 105,450,231,154 instructions # 1.46 insn per cycle ( +- 0.01% ) - 5,878,232,620 ns duration_time ( +- 0.38% ) + 5,290,085,069 ns duration_time ( +- 0.21% ) - 5.8782 +- 0.0221 seconds time elapsed ( +- 0.38% ) + 5.2901 +- 0.0111 seconds time elapsed ( +- 0.21% ) Build time improvement of -11.1% (duration_time) is expected: the parallel build time of the scheduler subsystem is determined by the largest, slowest to build object file, which is kernel/sched/core.o. By moving ~15% of its complexity into another build unit, we reduced build time by -11%. Measured cycles spent on building is within its ~0.2% stddev noise envelope. The -0.7% reduction in instructions spent on building the scheduler is statistically reliable and somewhat surprising - I can only speculate: maybe compilers aren't that efficient at building & optimizing 10+ KLOC files (core.c), and it's an overall win to balance the linecount a bit. Anyway, this might be a data point that suggests that reducing the linecount of our largest files will improve not just code readability and maintainability, but might also improve build times a bit. Code generation got a bit worse, by 0.5kb text on an x86 defconfig build: # -Before/+After: kepler:~/tip> size vmlinux text data bss dec hex filename -26475475 10439178 1740804 38655457 24dd5e1 vmlinux +26476003 10439178 1740804 38655985 24dd7f1 vmlinux kepler:~/tip> size kernel/sched/built-in.a text data bss dec hex filename - 76056 30025 489 106570 1a04a kernel/sched/core.o (ex kernel/sched/built-in.a) + 63452 29453 489 93394 16cd2 kernel/sched/core.o (ex kernel/sched/built-in.a) 44299 2181 104 46584 b5f8 kernel/sched/fair.o (ex kernel/sched/built-in.a) - 42764 3424 120 46308 b4e4 kernel/sched/build_policy.o (ex kernel/sched/built-in.a) + 55651 4044 120 59815 e9a7 kernel/sched/build_policy.o (ex kernel/sched/built-in.a) 44866 12655 2192 59713 e941 kernel/sched/build_utility.o (ex kernel/sched/built-in.a) 44866 12655 2192 59713 e941 kernel/sched/build_utility.o (ex kernel/sched/built-in.a) This is primarily due to the extra functions exported, and the size gets exaggerated somewhat by __pfx CFI function padding: ffffffff810cc710 <__pfx_enqueue_task>: ffffffff810cc710: 90 nop ffffffff810cc711: 90 nop ffffffff810cc712: 90 nop ffffffff810cc713: 90 nop ffffffff810cc714: 90 nop ffffffff810cc715: 90 nop ffffffff810cc716: 90 nop ffffffff810cc717: 90 nop ffffffff810cc718: 90 nop ffffffff810cc719: 90 nop ffffffff810cc71a: 90 nop ffffffff810cc71b: 90 nop ffffffff810cc71c: 90 nop ffffffff810cc71d: 90 nop ffffffff810cc71e: 90 nop ffffffff810cc71f: 90 nop AFAICS the cost is primarily not to core.o and fair.o though (which contain most performance sensitive scheduler functions), only to syscalls.o that get called with much lower frequency - so I think this is an acceptable trade-off for better code separation. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Link: https://lore.kernel.org/r/20240407084319.1462211-2-mingo@kernel.org |
||
---|---|---|
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.