Ttgjyuk

I installed ubuntu 16.04 LTS in Oct. last year on my newly bought HP Envy i7-6700 CPU (x64-based 3.4GHz 4-core 8 -processors, 16 GB ram, 2TB hard drive), it was running OK until just before the X-mas holidays when it became very slow, some times grey window frame. It seems stuck somewhere.

I have Ubuntu 16.04 running on a Dell Precision M4800. Today, my system suddenly became extremely slow. Googling the issue brought me here.

I fixed the issue by booting into the BIOS and disabling some of the power management features designed to reduce CPU power consumption when there is little work to do. After rebooting into Ubuntu, my system is running as fast as normal again.

I had this issue with a previous laptop as well-- somehow, it seems like it's possible for Ubuntu to get the Intel CPU "stuck" in a low-power, low-performance configuration permanently.

As the other answer, my solution was to disable SpeedStep on the BIOS. I found out that the my cpu was running slower. My CPU should run at 1800MHz, but is was running at 1000MHz. You can see the current CPU speed using several shell commands, e.g:

lscpu

or

cat /proc/cpu

It seems there was a problem with my charger and that made Ubuntu put the CPU into low consumption mode.

when its slow issue this in a terminal window ( ctrl-alt-t ) to display top resource using processes

top

here is the output ... notice load average at right of first row

top - 11:48:11 up 3 days, 8 min, 1 user, load average: 0.23, 0.39, 0.54
Tasks: 276 total, 1 running, 272 sleeping, 0 stopped, 3 zombie
%Cpu(s): 1.8 us, 0.7 sy, 0.0 ni, 95.2 id, 2.3 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 16326792 total, 6946732 free, 1726764 used, 7653296 buff/cache
KiB Swap: 16669692 total, 16669692 free, 0 used. 13860968 avail Mem 

 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 
17093 stens 20 0 1629772 446180 121904 S 5.6 2.7 137:51.51 firefox 
14358 stens 20 0 1390800 420448 113728 S 4.2 2.6 0:35.42 Web Content 
 1219 etcd 20 0 639392 28764 12468 S 2.8 0.2 9:24.84 etcd 
 1531 root 20 0 470212 72960 56564 S 1.4 0.4 25:49.02 Xorg 
 2718 stens 20 0 1266236 112712 61796 S 1.4 0.7 52:15.46 compiz 
 2757 stens 20 0 506036 25220 19440 S 1.4 0.2 32:02.48 indicator-multi 
 3228 stens 20 0 712920 69960 35624 S 1.4 0.4 2:51.65 gnome-terminal- 
 3488 root 20 0 251432 53740 24132 S 1.4 0.3 5:33.92 mongod 
13335 root 20 0 0 0 0 S 1.4 0.0 0:01.17 kworker/u16:3 

typically it will appear slow once load average gets over 5 or so YMMV ... listed under COMMAND is the ordered column of top resource consumers ... when its slow kill off whichever process is slowing it down to confirm you found the bad behaving process ... while running top it will autorefresh every few seconds yet if in a hurry hit the spacebar to force a refresh ... hitting key m will focus attention on showing Memory hungry processes ... to kill off the top most resource consuming process just hit key k from which you can enter options or just hit enter

Above has nothing to do with being slow due to insufficient internet bandwidth. If by slow you mean the browser is slow then a simple check is http://beta.speedtest.net/

Alternatives to top are

htop
atop 
iotop 

Another route to investigate slowness is see if system errors are getting kicked down into system log ... issue

dmesg

look for entries (to scroll up in terminal hold down shift then hit key page up ... or roll mouse middle roller button ) important entries are shown in red or appear error related then research on them ... if you are running some rogue driver not tuned to your hardware or fails to play well with others then its conflicting behaviour can manifest in slowness ... to empty out prior entries issue

sudo dmesg -c

to setup a real time monitor of dmesg issue

watch "dmesg | tail -20"

Here are more logs to examine

cat /var/log/syslog

cat /var/log/kern.log 

Let us know how you get on - this is certainly solvable ... a major advantage of linux is its efficient use of hardware as well as its ability to give at hand controls to adjust everything

Install package called i7z and run it. It will show you whether your cpu is running at full speed and cpu throttling (=lower speed) is not active.