Showing posts from February, 2018

Handling out of memory (OOM) in embedded systems without swap

Background Swap is a logical and slow extension of physical RAM. Whenever the system runs out of the physical RAM, the Linux kernel writes the least used data from RAM to swap in turn freeing up some RAM. Typically, swap is setup on a separate dedicated partition on secondary storage or a separate storage itself. Sometimes, specially created files on an existing filesystem are also used as swap. A lot of embedded systems use NAND flashes or SSDs as their secondary storage drives. These devices are typically divided in fixed size blocks. The blocks needs to be erased before they can be written to again. These devices don’t have mechanical parts in them which fails them. Its their write/erase or program/erase cycles that age them out. The write/erase cycles are limited on these devices which define their age. This property makes them unsuitable to be used as a swap device. The Problem Sometime ago, I faced an out of memory problem on a project I was working on