Linux network source code analysis (1)

When analyzing the Linux source code today, we can see that net_device {} has a ____ cacheline_aligned_in_smp.

____ Cacheline_aligned_in_smp is defined in include/Linux/cache. h:

#ifndef ____cacheline_aligned
#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
#endif

#ifndef ____cacheline_aligned_in_smp
#ifdef CONFIG_SMP
#define ____cacheline_aligned_in_smp ____cacheline_aligned
#else
#define ____cacheline_aligned_in_smp
#endif /* CONFIG_SMP */
#endif

#ifndef __cacheline_aligned
#define __cacheline_aligned                    \
__attribute__((__aligned__(SMP_CACHE_BYTES),            \
__section__(".data.cacheline_aligned")))
#endif /* __cacheline_aligned */

#ifndef __cacheline_aligned_in_smp
#ifdef CONFIG_SMP
#define __cacheline_aligned_in_smp __cacheline_aligned
#else
#define __cacheline_aligned_in_smp
#endif /* CONFIG_SMP */
#endif

/*
* The maximum alignment needed for some critical structures
* These could be inter-node cacheline sizes/L3 cacheline
* size etc.  Define this in asm/cache.h for your arch
*/
#ifndef INTERNODE_CACHE_SHIFT
#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
#endif

#if !defined(____cacheline_internodealigned_in_smp)
#if defined(CONFIG_SMP)
#define ____cacheline_internodealigned_in_smp \
__attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
#else
#define ____cacheline_internodealigned_in_smp
#endif
#endif