Smarter write throttling

Smarter write throttling

Posted Aug 19, 2007 1:48 UTC (Sun) by giraffedata (subscriber, #1954)
In reply to: Smarter write throttling by i3839
Parent article: Smarter write throttling

What is throttled here is the speed of dirtying pages,

Actually, nothing is throttled here. Rather, the amount of memory made available for writebehind buffering is restricted, so folks have to wait for it. Tightening resource availability slows down users of resources, like throttling would, but it's a fundamentally different concept. Resource restriction pushes back from the actual source of the problem (scarce memory), whereas throttling makes the requester of resource just ask for less, based on some higher level determination that the resource manager would give him too much.

I think the article is really about smarter memory allocation for writebehind data, not smarter write throttling.

(To understand the essence of throttling, I think it's good to look at the origin of the word. It means to choke, as in squeezing a tube (sometimes a person's throat) to reduce flow through it. The throttle of a classic gas engine prevents the fuel system from delivering fuel to the engine even though the engine is able to burn it).

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