c8afaa1b0f
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>
62 lines
1.5 KiB
C
62 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* include/asm-alpha/processor.h
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*
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* Copyright (C) 1994 Linus Torvalds
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*/
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#ifndef __ASM_ALPHA_PROCESSOR_H
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#define __ASM_ALPHA_PROCESSOR_H
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#include <linux/personality.h> /* for ADDR_LIMIT_32BIT */
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/*
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* We have a 42-bit user address space: 4TB user VM...
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*/
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#define TASK_SIZE (0x40000000000UL)
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#define STACK_TOP \
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(current->personality & ADDR_LIMIT_32BIT ? 0x80000000 : 0x00120000000UL)
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#define STACK_TOP_MAX 0x00120000000UL
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/* This decides where the kernel will search for a free chunk of vm
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* space during mmap's.
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*/
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#define TASK_UNMAPPED_BASE \
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((current->personality & ADDR_LIMIT_32BIT) ? 0x40000000 : TASK_SIZE / 2)
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/* This is dead. Everything has been moved to thread_info. */
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struct thread_struct { };
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#define INIT_THREAD { }
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/* Do necessary setup to start up a newly executed thread. */
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struct pt_regs;
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extern void start_thread(struct pt_regs *, unsigned long, unsigned long);
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/* Free all resources held by a thread. */
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struct task_struct;
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unsigned long __get_wchan(struct task_struct *p);
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#define KSTK_EIP(tsk) (task_pt_regs(tsk)->pc)
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#define KSTK_ESP(tsk) \
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((tsk) == current ? rdusp() : task_thread_info(tsk)->pcb.usp)
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#define cpu_relax() barrier()
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#define ARCH_HAS_PREFETCH
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#define ARCH_HAS_PREFETCHW
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extern inline void prefetch(const void *ptr)
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{
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__builtin_prefetch(ptr, 0, 3);
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}
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extern inline void prefetchw(const void *ptr)
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{
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__builtin_prefetch(ptr, 1, 3);
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}
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#endif /* __ASM_ALPHA_PROCESSOR_H */
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