linux/arch/sparc
Mateusz Guzik c8afaa1b0f locking: remove spin_lock_prefetch
The only remaining consumer is new_inode, where it showed up in 2001 as
commit c37fa164f793 ("v2.4.9.9 -> v2.4.9.10") in a historical repo [1]
with a changelog which does not mention it.

Since then the line got only touched up to keep compiling.

While it may have been of benefit back in the day, it is guaranteed to
at best not get in the way in the multicore setting -- as the code
performs *a lot* of work between the prefetch and actual lock acquire,
any contention means the cacheline is already invalid by the time the
routine calls spin_lock().  It adds spurious traffic, for short.

On top of it prefetch is notoriously tricky to use for single-threaded
purposes, making it questionable from the get go.

As such, remove it.

I admit upfront I did not see value in benchmarking this change, but I
can do it if that is deemed appropriate.

Removal from new_inode and of the entire thing are in the same patch as
requested by Linus, so whatever weird looks can be directed at that guy.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/fs/inode.c?id=c37fa164f793735b32aa3f53154ff1a7659e6442 [1]
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-08-12 09:18:47 -07:00
..
boot kbuild: factor out the common installation code into scripts/install.sh 2022-05-11 21:45:53 +09:00
configs arch/*/configs/*defconfig: Replace AUTOFS4_FS by AUTOFS_FS 2023-07-29 14:08:22 -07:00
crypto crypto: Kconfig - simplify cipher entries 2022-08-26 18:50:43 +08:00
include locking: remove spin_lock_prefetch 2023-08-12 09:18:47 -07:00
kernel - Arnd Bergmann has fixed a bunch of -Wmissing-prototypes in 2023-06-28 10:59:38 -07:00
lib bitops: wrap non-atomic bitops with a transparent macro 2022-06-30 19:52:41 -07:00
math-emu treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
mm sparc32: fix lock_mm_and_find_vma() conversion 2023-06-29 20:41:24 -07:00
net net: remove skb->vlan_present 2022-11-11 18:18:05 -08:00
power
prom sparc64: Replace all non-returning strlcpy with strscpy 2023-06-14 12:04:06 -07:00
vdso treewide: use get_random_u32_below() instead of deprecated function 2022-11-18 02:15:15 +01:00
video arch/sparc: Add module license and description for fbdev helpers 2023-06-29 13:30:02 +02:00
Kbuild kbuild: use more subdir- for visiting subdirectories while cleaning 2021-10-24 13:49:46 +09:00
Kconfig Merge branch 'expand-stack' 2023-06-28 20:35:21 -07:00
Kconfig.debug watchdog/sparc64: define HARDLOCKUP_DETECTOR_SPARC64 2023-06-19 16:25:29 -07:00
Makefile Merge drm/drm-next into drm-misc-next 2023-05-09 15:03:40 +02:00