我使用的是带有 RT 补丁的定制 Linux 系统，并且还启用了LatencyTOP.在cyclictest阶段中，我使用d捕获延迟信息，发现有很多延迟，尤其是hrtimer_nanosleep和do_select，这正常吗？
＃1：
taskset -c 2 cyclictest -t 1 -p 80 -n -i 1000 -l 1000000000
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 1.45 1.25 0.75 1/131 4401
T: 0 ( 875) P:80 I:1000 C: 764021 Min: 2 Act: 4 Avg: 3 Max: 28
＃2：
cat /proc/latency_stats
Latency Top version : v0.1
549481 534022296 982 hrtimer_nanosleep common_nsleep_timens __x64_sys_clock_nanosleep do_syscall_64 entry_SYSCALL_64_after_hwframe
2191 1159065 1151 do_wait kernel_wait4 do_syscall_64 entry_SYSCALL_64_after_hwframe
4500 2626162 4999 do_select core_sys_select do_pselect.constprop.0 __x64_sys_pselect6 do_syscall_64 entry_SYSCALL_64_after_hwframe
76 38535 599 do_get_write_access jbd2_journal_get_write_access __ext4_journal_get_write_access ext4_reserve_inode_write __ext4_mark_inode_dirty ext4_dirty_inode __mark_inode_dirty touch_atime step_into path_openat do_filp_open do_open_execat
12 34 7 wait_transaction_locked add_transaction_credits start_this_handle jbd2__journal_start ext4_dirty_inode __mark_inode_dirty touch_atime filemap_read __kernel_read bprm_execve do_execveat_common.isra.0 __x64_sys_execve
4 170 43 usb_start_wait_urb usb_control_msg f81604_get_register [f81604] f81604_get_berr_counter [f81604] can_fill_info [can_dev] rtnl_fill_ifinfo rtnl_dump_ifinfo netlink_dump netlink_recvmsg ____sys_recvmsg ___sys_recvmsg __sys_recvmsg
4 198 76 usb_start_wait_urb usb_control_msg f81604_get_register [f81604] f81604_get_berr_counter [f81604] can_fill_info [can_dev] rtnl_fill_ifinfo rtnl_dump_ifinfo netlink_dump netlink_recvmsg ____sys_recvmsg ___sys_recvmsg __sys_recvmsg
3 21 15 __flush_work.isra.0 n_tty_poll tty_poll do_select core_sys_select do_pselect.constprop.0 __x64_sys_pselect6 do_syscall_64 entry_SYSCALL_64_after_hwframe