Interesting, enjoying, and even funny technical read from Poul-Henning Kamp: Architect Notes for the Varnish HTTP Accelerator
His big point is that programmers need to stop fretting over moving things between memory and disk themselves. He explains that on a modern computer system, RAM is backed by disk, and disk accesses are buffered in RAM, and a lot of work goes in to the kernel to ensure that the system behaves effectively. By managing your own RAM-or-disk conundrum, you end up making a mess of things, because when you go to move an unused “memory” object to disk, the kernel may already have paged the memory region to disk, and what happens is the object then must move from virtual memory on disk, to RAM, to a disk memory cache in RAM, and then back out to disk. It is simpler and more efficient to just ask for a big chunk of memory and let the kernel page things to disk for you.
He then explains some clever things you can do for multi-processor programming. It seems to boil down to trying to give threads their own stack space wherever practical, and managing worker pools as a stack, so that you are most likely to find yourself processing on the same CPU at the lowest level of cache, and least likely to need to pass memory variables between CPUs.
Not that I write multi-threaded applications, but if I ever do, I’ll try to keep this understanding in mind.
[NOTE: For some time I have been considering a series of short “Deathmatch” style articles, contrasting similar-but-different words. This post is the “Pilot” for such a series.]
A geek speculates: what is the difference between a CIO and a CTO?
Google returns a lengthy definition, a Slashdot discussion, and other answers. But Sean enjoyed my answer: (more…)
Inhabitat has an informative and lightheartedly disturbing visit with the “Sustainable Agriculture Production and Research Center” at Disney World’s EPCOT center. The overall gist of the place is good old fashioned 1950s optimism that technology will make the future awesome, touched up a layer of 21st century “green washing”.
Next stop on the “Living With the Land” tour took us up close and personal with stacked gardens. While we love the idea of maximizing space and efficiency by vertically stacking plants, we can’t figure out why on earth a greenhouse preaching sustainability uses STYROFOAM pots for all their plants! A precocious 6-year-old boy on my tour apparently noticed the same thing and asked our intern-guide why there was so much styrofoam, since the foam plastic is not biodegradable and not really a “sustainable” choice for an exhibit on sustainability. Our guide, apparently not understanding the implications of the question, explained glibly that EPCOT uses styrofoam because it is cheap, lightweight and easy to toss out in order to get fresh new pots daily. Huh?
The primary byproduct of the sustainable “Research Center” seems to be genetically-modified vegetables grown in the shape of Mickey Mouse’s head. Well, that and the styrofoam containers.
I had a friend from Indiana who said she knew someone from Florida, who thought that, compared to Governor Jeb, President George was oh-so-eloquent. I suppose it is fortunate that the state will mostly disappear when the ice caps melt.