Chapter3:MemoryManagement
the alignment factor as long as this is possible for the given object size. As a result, 2, 4,...objects fit into
a cache line instead of a single object.
mm/slab.c
/* 1) arch recommendation: */
if (flags & SLAB_HWCACHE_ALIGN) {
/* Default alignment: as specified by the arch code.
* Except if an object is really small, then squeeze multiple
* objects into one cacheline.
*/
ralign = cache_line_size();
while (size <= ralign/2)
ralign /= 2;
} else {
ralign = BYTES_PER_WORD;
}
...
Sanity checks
Calculate alignment
Allocate cache structure
Determine where to store slab head
Compute cache size iteratively with cache_estimate
Compute colors
Insert cache in cache_chain
kmem_cache_create
calculate_slab_order
enable_cpucache do_tune_cpucache
Figure 3-49: Code flow diagram forkmem_cache_create.
The kernel also takes account of the fact that some architectures require a minimum boundary for
the alignment of data as defined byARCH_SLAB_MINALIGN; the alignment required by users is also
accepted.
mm/slab.c
/* 2) arch mandated alignment */
if (ralign < ARCH_SLAB_MINALIGN) {
ralign = ARCH_SLAB_MINALIGN;
}
/* 3) caller mandated alignment */
if (ralign < align) {
