linux/include
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
..
acpi More ACPI updates for 6.5-rc1 2023-07-06 22:25:06 -07:00
asm-generic hyperv-fixes for 6.5-rc5 2023-08-04 17:16:14 -07:00
clocksource
crypto This update includes the following changes: 2023-06-30 21:27:13 -07:00
drm drm/fb-helper: Remove unused inline function drm_fb_helper_defio_init() 2023-07-25 20:38:37 +02:00
dt-bindings Another set of clk driver updates and fixes for the merge window. The 2023-07-04 11:07:45 -07:00
keys
kunit
kvm KVM: arm64: vgic-v4: Make the doorbell request robust w.r.t preemption 2023-07-13 22:23:34 +00:00
linux locking: remove spin_lock_prefetch 2023-08-12 09:18:47 -07:00
math-emu
media media updates for v6.5-rc1 2023-07-05 10:42:32 -07:00
memory
misc
net netfilter pull request 23-08-10 2023-08-10 10:47:08 -07:00
pcmcia
ras
rdma rdma: fix INFINIBAND_USER_ACCESS dependency 2023-07-03 16:55:04 -07:00
rv
scsi ata,scsi: do not issue START STOP UNIT on resume 2023-08-02 17:01:12 +09:00
soc Memory controller drivers - fixes for v6.5 2023-07-27 15:40:54 +02:00
sound
target SCSI misc on 20230629 2023-06-30 11:57:07 -07:00
trace tcp: add missing family to tcp_set_ca_state() tracepoint 2023-08-09 13:45:19 -07:00
uapi Including fixes from bpf and wireless. 2023-08-03 14:00:02 -07:00
ufs Merge branch '6.5/scsi-staging' into 6.5/scsi-fixes 2023-07-11 12:15:15 -04:00
vdso
video
xen xen/evtchn: Introduce new IOCTL to bind static evtchn 2023-07-26 08:42:34 +02:00