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linux kernel development, 3rd edition

robert love2010

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2017-10-22

processes

continuing on linux kernel development, 3rd edition by robert love. on the first pass, i'm just getting a general overview. so here's a general overview of processes in linux:

the photo shows a few of the processes running on my machine. uid is the user id, which is me, i guess. pid is the process id. ppid is the parent process id. linux generates new processes by forking, and you'll notice a lot of processes have kthreadd as their parent -- this is the kernel thread daemon.

then you have rtprio - real time priority - and ni - nice value. both relate to the same idea -- how willing is a process to give some of its share of processor time to others. the -20 nice values are not nice -- kworker wants as much time as it can get. 0 is the default in user space. 19 is the nicest value.

love talked about the trade-offs and issues involved in multitasking. fast process switching means no process has to wait long for its turn, but increases overhead. some processes are processor-bound (mostly for crunching numbers and the like), some are i/o-bound (a text editor spends most of the time waiting for keys to be typed). a smart kernel has to get both types appropriate segments of time.