On Thursday 24 July 2008, b.n. wrote: > > I jump here to relief my everlasting UNIX ignorance. > > What does it mean a process is "sleeping", technically?
It's a misnomer, it means "not running". The cpu gives the illusion of executing many tasks simultaneously. In reality, it is executing them one at a time and very rapidly (many times a second) switching between them. Normally at a given instant in time, one task is running per cpu. The rest are mostly waiting their turn or sleeping. There are various OS strategies for bringing this about - some rely on the task itself to back out after a running for a short while, sometimes the OS kernel enforces it, sometimes you have a combination. If everything is working nicely, the end result is pretty much the same. There's another state worthy of note - blocked. This is when a task is waiting for something else to happen first (most often disk or network I/O) so it won't try and execute till that other thing happens. This is not the same as sleeping. Sleeping is spinning you wheels in idle, blocked is a deliberate stop and sit back and wait. hth alan -- Alan McKinnon alan dot mckinnon at gmail dot com
