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| author | Mateusz Guzik <mjguzik@gmail.com> | 2023-08-12 19:15:54 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-08-12 19:18:47 +0300 |
| commit | c8afaa1b0f8bc93d013ab2ea6b9649958af3f1d3 (patch) | |
| tree | cdf2d4c2f22ab40d7d31ba99ffdce18e3dfcc6cd /arch/x86/include | |
| parent | 3feecb1b848359b152dd66b26c24c2454a64fc15 (diff) | |
| download | linux-c8afaa1b0f8bc93d013ab2ea6b9649958af3f1d3.tar.xz | |
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>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 6 |
1 files changed, 0 insertions, 6 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 4ae2773b873d..fd750247ca89 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -586,7 +586,6 @@ extern char ignore_fpu_irq; #define HAVE_ARCH_PICK_MMAP_LAYOUT 1 #define ARCH_HAS_PREFETCHW -#define ARCH_HAS_SPINLOCK_PREFETCH #ifdef CONFIG_X86_32 # define BASE_PREFETCH "" @@ -620,11 +619,6 @@ static __always_inline void prefetchw(const void *x) "m" (*(const char *)x)); } -static inline void spin_lock_prefetch(const void *x) -{ - prefetchw(x); -} - #define TOP_OF_INIT_STACK ((unsigned long)&init_stack + sizeof(init_stack) - \ TOP_OF_KERNEL_STACK_PADDING) |