So my computer boots up for 150s and I can clearly see that it does nothing between 40-105s. Can You help me determine which process is responsible for this waste of time?
I can clearly see that it does nothing between 40-105s.
If you mean, the CPU usage appears low, notice that 'I/O (wait)' is very high during that time period, and a number of processes are shaded pink (at least one for the entire period), indicating they are in "interruptible sleep".
Uninterruptible sleep is not necessarily a passive state for the kernel -- it may be busy looping the whole time, and this is normally included in the "sys" component of CPU time, so perhaps the app which produced this graph has subtracted that. In any case, if the boot process has reached a point where nothing more can start because everything remaining requires something else to finish first, and those things are all waiting on I/O, then this is what could happen.
If this is a normal desktop using local disk storage, uninterruptible I/O waits this long may indicate intermittently failing hardware.