Kernel space: How much memory am I really using?
nybody who has tried to figure out why a Linux system is running short of memory can attest that the memory usage information made available by the kernel is, at best, difficult to use. Matt Mackall has recently been working on a set of patches aimed at improving this situation. Given the constraints imposed by embedded Linux systems, it is not surprising that Matt chose the Embedded Linux Conference to present his work (which, incidentally, was funded by the Consumer Electronics Linux Forum).Matt pointed out that the currently-available information is confusing at best. The page cache muddies the situation, and the sharing of pages between applications complicates things even more. The result is that it is hard to say where memory is being used; one can’t even get a definitive answer to the question of how big a specific application is. More detailed questions - such as which parts of an application are using the most memory - are even harder to answer. Trying to answer questions of interest to embedded systems developers - how many applications can run on a specific device without pushing it into thrashing, for example - is nearly impossible without simply running a test.
The problem is that the numbers exported by the current kernels are nearly meaningless.
