On 3/20/2019 7:53 PM, Matthew Wilcox wrote: > On Wed, Mar 20, 2019 at 09:48:47AM +0100, Vlastimil Babka wrote: >> Natural alignment to size is rather well defined, no? Would anyone ever >> assume a larger one, for what reason? >> It's now where some make assumptions (even unknowingly) for natural >> There are two 'odd' sizes 96 and 192, which will keep cacheline size >> alignment, would anyone really expect more than 64 bytes? > > Presumably 96 will keep being aligned to 32 bytes, as aligning 96 to 64 > just results in 128-byte allocations. Well, looks like that's what happens. This is with SLAB, but the alignment calculations should be common: slabinfo - version: 2.1 # name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> <batchcount> <sharedfactor> : slabdata <active_slabs> <num_slabs> <sharedavail> kmalloc-96 2611 4896 128 32 1 : tunables 120 60 8 : slabdata 153 153 0 kmalloc-128 4798 5536 128 32 1 : tunables 120 60 8 : slabdata 173 173 0
