forked from mirrors/linux
e6ad640bc4
There are three users (mmzone.h, memcontrol.h, page_counter.h) using similar code for forcing cacheline padding between fields of different structures. Dedup that code. Link: https://lkml.kernel.org/r/20220826230642.566725-1-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Suggested-by: Feng Tang <feng.tang@intel.com> Reviewed-by: Feng Tang <feng.tang@intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
101 lines
2.9 KiB
C
101 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_CACHE_H
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#define __LINUX_CACHE_H
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#include <uapi/linux/kernel.h>
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#include <asm/cache.h>
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#ifndef L1_CACHE_ALIGN
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#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
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#endif
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#ifndef SMP_CACHE_BYTES
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#define SMP_CACHE_BYTES L1_CACHE_BYTES
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#endif
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/*
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* __read_mostly is used to keep rarely changing variables out of frequently
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* updated cachelines. Its use should be reserved for data that is used
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* frequently in hot paths. Performance traces can help decide when to use
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* this. You want __read_mostly data to be tightly packed, so that in the
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* best case multiple frequently read variables for a hot path will be next
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* to each other in order to reduce the number of cachelines needed to
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* execute a critical path. We should be mindful and selective of its use.
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* ie: if you're going to use it please supply a *good* justification in your
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* commit log
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*/
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#ifndef __read_mostly
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#define __read_mostly
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#endif
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/*
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* __ro_after_init is used to mark things that are read-only after init (i.e.
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* after mark_rodata_ro() has been called). These are effectively read-only,
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* but may get written to during init, so can't live in .rodata (via "const").
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*/
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#ifndef __ro_after_init
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#define __ro_after_init __section(".data..ro_after_init")
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#endif
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#ifndef ____cacheline_aligned
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#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
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#endif
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#ifndef ____cacheline_aligned_in_smp
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#ifdef CONFIG_SMP
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#define ____cacheline_aligned_in_smp ____cacheline_aligned
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#else
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#define ____cacheline_aligned_in_smp
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#endif /* CONFIG_SMP */
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#endif
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#ifndef __cacheline_aligned
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#define __cacheline_aligned \
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__attribute__((__aligned__(SMP_CACHE_BYTES), \
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__section__(".data..cacheline_aligned")))
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#endif /* __cacheline_aligned */
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#ifndef __cacheline_aligned_in_smp
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#ifdef CONFIG_SMP
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#define __cacheline_aligned_in_smp __cacheline_aligned
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#else
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#define __cacheline_aligned_in_smp
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#endif /* CONFIG_SMP */
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#endif
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/*
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* The maximum alignment needed for some critical structures
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* These could be inter-node cacheline sizes/L3 cacheline
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* size etc. Define this in asm/cache.h for your arch
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*/
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#ifndef INTERNODE_CACHE_SHIFT
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#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
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#endif
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#if !defined(____cacheline_internodealigned_in_smp)
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#if defined(CONFIG_SMP)
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#define ____cacheline_internodealigned_in_smp \
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__attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
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#else
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#define ____cacheline_internodealigned_in_smp
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#endif
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#endif
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#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
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#define cache_line_size() L1_CACHE_BYTES
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#endif
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/*
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* Helper to add padding within a struct to ensure data fall into separate
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* cachelines.
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*/
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#if defined(CONFIG_SMP)
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struct cacheline_padding {
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char x[0];
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} ____cacheline_internodealigned_in_smp;
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#define CACHELINE_PADDING(name) struct cacheline_padding name
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#else
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#define CACHELINE_PADDING(name)
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#endif
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#endif /* __LINUX_CACHE_H */
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