keep it fresh. keep it fun
Oh, the things you can schedule,
the games you can play!
If you keep a clear head, you’ll
be well on your way.
You start with a blank sheet,
three nuts and a bolt,
a strong sense of fairness,
a large can of Jolt.
Continue reading “The Thread in the Head: Dr Sqlos explains context switching”
ARTHUR: Who lives in that castle?
WOMAN: No one lives there.
ARTHUR: Then who is your lord?
WOMAN: We don’t have a lord.
ARTHUR: What?
DENNIS: I told you. We’re an anarcho-syndicalist commune. We take it in turns to act as a sort of executive officer for the week.
(from Monty Python and the Holy Grail)
Picture a world consisting of forty Energizer bunnies, grouped into four teams of ten. Each team has one battery between them, and the main rule of the game is that each bunny may only use the battery for a little while before transferring it to a teammate. There is no way for a sleeping player to be woken up except by being passed the battery, and each battery strictly stays within one team.
Continue reading “King Arthur, Energizer bunnies, and the search for the SQLOS scheduler”
SystemThread, a class within sqldk.dll, can be considered to be at the root of SQLOS’s scheduling capabilities. While it doesn’t expose much obviously exciting functionality, it encapsulates a lot of the state that is necessary to give a thread a sense of self in SQLOS, serving as the beacon for any code to find its way to an associated SQLOS scheduler etc. I won’t go into much of the SQLOS object hierarchy here, but suffice it to say that everything becomes derivable by knowing one’s SystemThread. As such, this class jumps the gap between a Windows thread and the object-oriented SQLOS.
Continue reading “Unsung SQLOS: the SystemThread”