如何检查尿素头是否起作用

我旋转了5400 rpm 1Gb驱动器。

引导需要69秒（很慢吗？），并且/var/lib/ureadahead包含空目录debugfs。这就是为什么我想知道尿素黑头是否能发挥作用。

/var 目录在根分区上

~ > df
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda7        24G   15G  8,1G  65% /
udev            3,9G  4,0K  3,9G   1% /dev
/dev/sda9       705G  143G  562G  21% /data
/dev/sda8        29G   24G  4,2G  85% /home

配置似乎是默认的

~ > cat /etc/init/ureadahead.conf|grep -v '#'|grep -ve '^$'
description "Read required files in advance"
start on starting mountall
stop on stopped rc
expect fork
kill timeout 180
normal exit 0
exec /sbin/ureadahead --daemon
pre-stop exec sleep 45

~ > cat /etc/init/ureadahead-other.conf|grep -v '#'|grep -ve '^$'
description "Read required files in advance (for other mountpoints)"
start on mounted DEVICE=[/UL]* MOUNTPOINT=/?*
expect fork
normal exit 0 4
exec /sbin/ureadahead --daemon $MOUNTPOINT

Strangily /var/log/upstart/ureadahead.log.1.gz几乎只包含“忽略的相对路径”或“没有这样的文件或目录”标记的条目。

root:/var/log# zcat upstart/ureadahead.log.1.gz |grep -v "Ignored relative path"
Counted 4 CPUs

ureadahead:/data/swapfile: Error retrieving chunk extents: Operation not supported
ureadahead:/var/lib/NetworkManager/dhclient-eth0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-wlan0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-eth0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-wlan0.conf: No such file or directory
ureadahead:/etc/X11/xorg.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-eth0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-wlan0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-eth0.conf: No such file or directory
ureadahead:/var/lib/NetworkManager/dhclient-wlan0.conf: No such file or directory
ureadahead:/usr/share/X11/xorg.conf.d/20-intel.conf: No such file or directory
Counted 4 CPUs

ureadahead:/data/swapfile: Error retrieving chunk extents: Operation not supported

在bootchart上，尿素黑头出现在第16秒，持续时间不到一秒。与/superuser/286571/ubuntu-slow-startup-time-modprobe进行比较，尿素头在普利茅斯之后立即开始

更新1添加blockdev报告

# blockdev --report
RO    RA   SSZ   BSZ   StartSec            Size   Device
rw   256   512  4096          0   1000204886016   /dev/sda
rw   256   512  4096       2048       524288000   /dev/sda1
rw   256   512  4096    1026048        41943040   /dev/sda2
rw   256   512  4096    1107968       134217728   /dev/sda3
rw   256   512  4096    1370112       524288000   /dev/sda4
rw   256   512  4096    2394112    171795546112   /dev/sda5
rw   256   512  4096 1927233536     13460267008   /dev/sda6
rw   256   512  4096  337932288     26214400000   /dev/sda7
rw   256   512  4096  389132288     31457280000   /dev/sda8
rw   256   512  4096  450572288    756050558976   /dev/sda9
rw   256   512   512          0      1073741312   /dev/sr0

分区/ dev / sda1-/ dev / sda / 6是windoze，ESP，DIAGS，WINRETOOLS，PBR映像

至少从2015年初开始，这种版本的Uradadahead就已经存在了，我怀疑它是在系统化的基础上编写的。我不知道次版本有何改变，但最近一次提交是在2010年。由于您的版本正在报告cpu计数，因此它们可能包括一些合并请求。

开发人员现在正在为Google工作。

此时最好的选择是禁用它。如果要减少启动几秒钟的时间，请删除wpa_supplicant（如果不需要）。