~# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
tracefs on /sys/kernel/debug/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)

~# ls /sys/fs
aufs  bpf  btrfs  cgroup  ecryptfs  ext4  fuse  pstore  xfs

~# ls /sys/kernel/debug/
acpi   btrfs            dma_buf        fault_around_bytes  intel_powerclamp  mce      pkg_temp_thermal  pwm        sched_debug       suspend_stats  virtio-ports
aufs   cleancache       dri            frontswap           iosf_sb           mei0     pmc_core          ras        sched_features    sync           wakeup_sources
bdi    clear_warn_once  dynamic_debug  gpio                kprobes           opp      pm_genpd          regmap     sleep_time        tracing        x86
block  clk              extfrag        i2c_amd_pci_mp2     kvm               pinctrl  pm_qos            regulator  split_huge_pages  usb            zswap

~# ls /proc/sys
abi  debug  dev  fs  kernel  net  user  vm