6c036527a6
Add a new section called ".data.read_mostly" for data items that are read frequently and rarely written to like cpumaps etc. If these maps are placed in the .data section then these frequenly read items may end up in cachelines with data is is frequently updated. In that case all processors in an SMP system must needlessly reload the cachelines again and again containing elements of those frequently used variables. The ability to share these cachelines will allow each cpu in an SMP system to keep local copies of those shared cachelines thereby optimizing performance. Signed-off-by: Alok N Kataria <alokk@calsoftinc.com> Signed-off-by: Shobhit Dayal <shobhit@calsoftinc.com> Signed-off-by: Christoph Lameter <christoph@scalex86.org> Signed-off-by: Shai Fultheim <shai@scalex86.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
#ifndef __LINUX_CACHE_H
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#define __LINUX_CACHE_H
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#include <linux/kernel.h>
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#include <linux/config.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(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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#ifdef CONFIG_X86
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#define __read_mostly __attribute__((__section__(".data.read_mostly")))
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#else
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#define __read_mostly
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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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#if !defined(____cacheline_maxaligned_in_smp)
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#if defined(CONFIG_SMP)
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#define ____cacheline_maxaligned_in_smp \
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__attribute__((__aligned__(1 << (L1_CACHE_SHIFT_MAX))))
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#else
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#define ____cacheline_maxaligned_in_smp
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#endif
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#endif
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#endif /* __LINUX_CACHE_H */
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