At first, the question seems to be a little bit silly/confusing as the OS does the job of managing process execution.

However, I want to measure how much some processes are CPU/IO-bound and I feel like my OS is interfering on my experiments with, for instance, scheduled OS processes.

Take as an example the following situation: I ran the process A twice and got the following output from the tool "time" (time columns in seconds):

+---+-------+---------+-----------+---------+
|Run|Process|User Time|System Time|Wall time|
+---+-------+---------+-----------+---------+
|1  |A      |196.3    |5.12       |148.86   |
|2  |A      |190.79   |4.93       |475.46   |
+---+-------+---------+-----------+---------+

As we can see, although the user and sys time are similar, the elapsed time of both drastically changes (diff. of ~5 min). Feels like something in my environment caused some sort of contention.

I want to stop every possible background process/services to avoid any kind of noise during my experiments but I consider myself a novice/intermediate unix-user and I don't know how to guarantee this.

I'm using Linux 4.4.0-45-generic with Ubuntu 14.04 LTS 64 bit.

I really appreciate the assistance. If you guys need any missing information, I will promptly edit my post.

CPU Info

$ grep proc /proc/cpuinfo | wc -l
8
$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 60
Stepping:              3
CPU MHz:               4002.609
BogoMIPS:              7183.60
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              8192K
NUMA node0 CPU(s):     0-7