On Fri, Jun 21, 2024 at 12:27:50PM +0200, Sebastian Andrzej Siewior wrote: > The alloc_tag member has been added to task_struct at the very > beginning. This is a pointer and on 64bit architectures it forces 4 byte > padding after `ptrace' and then forcing another another 4 byte padding > after `on_cpu'. A few members later, `se' requires a cacheline aligned > due to struct sched_avg resulting in 52 hole before `se'. > > This is the case on 64bit-SMP architectures. > The 52 byte hole can be avoided by moving alloc_tag away where it > currently resides. > > Move alloc_tag to the end of task_struct. There is likely a hole before > `thread' due to its alignment requirement and the previous members are > likely to be already pointer-aligned. We sure we want it at the end? we do want it on a hot cacheline
