Comments on: Fractal Memory Usage and a Big Number http://www.algorithm.co.il/blogs/computer-science/fractal-memory-usage-and-a-big-number/ Algorithms, for the heck of it Tue, 21 Jun 2011 21:07:08 +0000 hourly 1 http://wordpress.org/?v=3.1.3 By: Aldrin Martoq http://www.algorithm.co.il/blogs/computer-science/fractal-memory-usage-and-a-big-number/#comment-131 Aldrin Martoq Tue, 16 Dec 2008 03:16:21 +0000 http://www.algorithm.co.il/blogs/?p=110#comment-131 Interesting post**post. About Ubuntu memory consumption: In Windows if a process ask for 2GB of RAM it is allocated immediatly ("sure, there you are" windows says) or refused ("sorry, i don't have enough memory right now"), but Linux instead always lies ("haha, ok" replies) and never allocates the amount of memory a process asks. The rationale behind this is that 99% of programs are badly written (which is sadly true), so they never actually USE the amount of memory they ask. So, as a program start to use the memory they asked, it becames allocated in the O.S, as the straight line you discovered. This is good most of the time, because unused memory becomes better used memory (disk cache for ex). The bad side is what happens if a program actually USE the 2GB they asked and memory is insufficient right now: well, Linux really will be an evil guy and will kill some "random" process. You can read a funny analogy in this LWN article: http://lwn.net/Articles/104179/ Interesting post**post.

About Ubuntu memory consumption: In Windows if a process ask for 2GB of RAM it is allocated immediatly (“sure, there you are” windows says) or refused (“sorry, i don’t have enough memory right now”), but Linux instead always lies (“haha, ok” replies) and never allocates the amount of memory a process asks.

The rationale behind this is that 99% of programs are badly written (which is sadly true), so they never actually USE the amount of memory they ask. So, as a program start to use the memory they asked, it becames allocated in the O.S, as the straight line you discovered.

This is good most of the time, because unused memory becomes better used memory (disk cache for ex). The bad side is what happens if a program actually USE the 2GB they asked and memory is insufficient right now: well, Linux really will be an evil guy and will kill some “random” process.

You can read a funny analogy in this LWN article:
http://lwn.net/Articles/104179/

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