该目录作为performance tuning应该很少用，除非安装了soft raid或开启SCSI日志
justin_$ pwd
/proc/sys/dev
justin_$ ls
cdrom hpet mac_hid parport raid scsi
先看scsi目录，只有一个参数logging_level
用于控制是否记录SCSI日志，0不激活1激活
justin_$ more logging_level
0
Raid目录包含两个参数
speed_limit_max /speed_limit_min
单位为k/s，当采用软件RAID时，可用于控制其I/O速率，当需要重建RAID时，可适当调大其参数
justin_$ more speed_limit_max
200000
justin_$ more speed_limit_min
1000
通过/proc/mdstat可以监控RAID重建进度
justin_$ more mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath]
md5 : active raid1 sde2[2](S) sdd2[3](S) sdc2[4](S) sdb2[1] sda2[0]
530048 blocks [2/2] [UU]
md0 : active raid6 sde3[4] sdd3[3] sdc3[2] sdb3[1] sda3[0]
5855836800 blocks level 6, 64k chunk, algorithm 2 [5/5] [UUUUU]
[============>........] resync = 61.7% (1205475036/1951945600) finish=242.9min speed=51204K/sec
Parport目录
其结构如下，用于设置并行设备的监测
parport
|-- default
| |-- spintime
| `-- timeslice
|-- parport0
| |-- autoprobe
| |-- autoprobe0
| |-- autoprobe1
| |-- autoprobe2
| |-- autoprobe3
| |-- devices
| | |-- active
| | `-- lp
| | `-- timeslice
| |-- base-addr
| |-- irq
| |-- dma
| |-- modes
| `-- spintime
`-- parport1
|-- autoprobe
|-- autoprobe0
|-- autoprobe1
|-- autoprobe2
|-- autoprobe3
|-- devices
| |-- active
| `-- ppa
| `-- timeslice
|-- base-addr
|-- irq
|-- dma
|-- modes
`-- spintime
/hpet目录
全称为high precision event timer，包含一个参数max-user-freq
justin_$ more max-user-freq
64
justin_$ dmesg | grep -i HPET
hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
hpet0: 4 comparators, 64-bit 14.318180 MHz counter
rtc0: alarms up to one year, y3k, 114 bytes nvram, hpet irqs
justin_$ cat /proc/driver/rtc
rtc_time : 09:57:06
rtc_date : 2013-02-02
alrm_time : **:**:**
alrm_date : ****-**-**
alarm_IRQ : no
alrm_pending : no
24hr : yes
periodic_IRQ : no
update_IRQ : no
HPET_emulated : yes
DST_enable : no
periodic_freq : 1024
batt_status : okay
http://blog.fpmurphy.com/2009/07/linux-hpet-support.html
http://docs.oracle.com/cd/E24290_01/coh.371/e22838/tune_perftune.htm#CACGHIEI