From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: signal: reorder struct sighand_struct struct sighand_struct::siglock field is the most used field by far, put it first so that is can be accessed without IMM8 or IMM32 encoding on x86_64. Space savings (on trimmed down VM test config): add/remove: 0/0 grow/shrink: 8/68 up/down: 49/-1147 (-1098) Function old new delta complete_signal 512 533 +21 do_signalfd4 335 346 +11 __cleanup_sighand 39 43 +4 unhandled_signal 49 52 +3 prepare_signal 692 695 +3 ignore_signals 37 40 +3 __tty_check_change.part 248 251 +3 ksys_unshare 780 781 +1 sighand_ctor 33 29 -4 ptrace_trap_notify 60 56 -4 sigqueue_free 98 91 -7 run_posix_cpu_timers 1389 1382 -7 proc_pid_status 2448 2441 -7 proc_pid_limits 344 337 -7 posix_cpu_timer_rearm 222 215 -7 posix_cpu_timer_get 249 242 -7 kill_pid_info_as_cred 243 236 -7 freeze_task 197 190 -7 flush_old_exec 1873 1866 -7 do_task_stat 3363 3356 -7 do_send_sig_info 98 91 -7 do_group_exit 147 140 -7 init_sighand 2088 2080 -8 do_notify_parent_cldstop 399 391 -8 signalfd_cleanup 50 41 -9 do_notify_parent 557 545 -12 __send_signal 1029 1017 -12 ptrace_stop 590 577 -13 get_signal 1576 1563 -13 __lock_task_sighand 112 99 -13 zap_pid_ns_processes 391 377 -14 update_rlimit_cpu 78 64 -14 tty_signal_session_leader 413 399 -14 tty_open_proc_set_tty 149 135 -14 tty_jobctrl_ioctl 936 922 -14 set_cpu_itimer 339 325 -14 ptrace_resume 226 212 -14 ptrace_notify 110 96 -14 proc_clear_tty 81 67 -14 posix_cpu_timer_del 229 215 -14 kernel_sigaction 156 142 -14 getrusage 977 963 -14 get_current_tty 98 84 -14 force_sigsegv 89 75 -14 force_sig_info 205 191 -14 flush_signals 83 69 -14 flush_itimer_signals 85 71 -14 do_timer_create 1120 1106 -14 do_sigpending 88 74 -14 do_signal_stop 537 523 -14 cgroup_init_fs_context 644 630 -14 call_usermodehelper_exec_async 402 388 -14 calculate_sigpending 58 44 -14 __x64_sys_timer_delete 248 234 -14 __set_current_blocked 80 66 -14 __ptrace_unlink 310 296 -14 __ptrace_detach.part 187 173 -14 send_sigqueue 362 347 -15 get_cpu_itimer 214 199 -15 signalfd_poll 175 159 -16 dequeue_signal 340 323 -17 do_getitimer 192 174 -18 release_task.part 1060 1040 -20 ptrace_peek_siginfo 408 387 -21 posix_cpu_timer_set 827 806 -21 exit_signals 437 416 -21 do_sigaction 541 520 -21 do_setitimer 485 464 -21 disassociate_ctty.part 545 517 -28 __x64_sys_rt_sigtimedwait 721 679 -42 __x64_sys_ptrace 1319 1277 -42 ptrace_request 1828 1782 -46 signalfd_read 507 459 -48 wait_consider_task 2027 1971 -56 do_coredump 3672 3616 -56 copy_process.part 6936 6871 -65 Link: http://lkml.kernel.org/r/20190503192800.GA18004@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/sched/signal.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/include/linux/sched/signal.h~signal-reorder-struct-sighand_struct +++ a/include/linux/sched/signal.h @@ -15,10 +15,10 @@ */ struct sighand_struct { - refcount_t count; - struct k_sigaction action[_NSIG]; spinlock_t siglock; + refcount_t count; wait_queue_head_t signalfd_wqh; + struct k_sigaction action[_NSIG]; }; /* _
