Admittedly, I am running on a build that is no younger than five years old at this point and the system is not going to be incredibly fast. However, at the same time, the run-times I am observing are so painfully slow it's urged me to create this question to see if there was something I could do to fix this problem. For example, I was simply unpacking a tarball, albeit quite a large one (~15GB), and the entire process took about 2.5 hours with about 9 minutes of actual CPU time. In contrast, the creation of this tarball took about just a few minutes. Again, the creation was on a fairly adept machine, but 2.5 hours seems far too slow. As a second example, building a particular project (on the adept machine) took only 19 seconds, with 17 of those seconds being actual CPU time. In contrast, the same process took nearly 9 minutes (on this slower machine) with only about 14 seconds being actual CPU time. As you can see below, the actual CPU time is fairly similar, it's just the total execution time that is the problem.Adept Machinereal    0m19.245suser    0m15.809ssys     0m0.908sCurrent Machinereal    8m37.500suser    0m11.175ssys     0m3.969sI include the unfair comparison between the two machines only as a reference point. There is nothing particularly amazing about the adept machine, it's just quite a bit newer. The current machine has 4 GB of RAM; the adept machine has quite a bit more as it is a server, but only 2 GB of RAM is actually being used. There's no disk I/O, the above performance happens when the machine is otherwise idle. Ubuntu in general tends to be quite a bit more sluggish than it should be, often times freezing for a few moments before resuming. Opening tasks tends to take a lot of time as well - as much as 20-30 seconds for something as simple as Eclipse; browsers can take 5-10 seconds as well.Ubuntu 14.04 -- Full-disk encryption enabledCore i-7 860 @ 2.8GhzWD2500JS 7200RPM SATA 3Gbps 8MB Cachetldr; Why is there such a huge gap between total execution time and actual CPU time? The disk I am using is not that slow. It's hard to believe the disk being the source of such a huge discrepancy. Perhaps it's the first-gen i7?Updates based on feedback in comments:Tried tar -t, but after 6 minutes of waiting I killed it. Total CPU time: 3 seconds in user space.taf -tf actually delivers output to the terminal and changes the output of iostat, but only 20-30 Kb/s.No error messages in the system log about filesystem corruption or disk timeoutsUnlike iostat, iotop actually gives results and shows 80-90% IO and 30-40 MB/s when listing contents with tar and redirecting it to /dev/null.
CPU Scheduling incredibly slow with large difference between total execution time and actual CPU time - Ubuntu Full-Disk Encryption enabled
ubuntu;cpu;scheduling;disk encryption