linux - Estimate the amount of RAM that can be allocated - Stack Overflow

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I would like to estimate the amount of allocatable memory in a system. On its outset, the question is very platform-dependent and next to impossible to answer. The concrete use case hopefully makes a sensible answer possible.

Before diving in, I note the possibility of an X-Y-problem. The real question is guessing a sensible parallelism for compiling code.

• Practically speaking, I'd like to know how much RAM can be allocated before something equivalent to Linux' out-of-memory killer kicks in. In case of a 32bit environment, the RAM may be distributed to multiple processes to avoid running into address space limits.
• The method should work on Linux, but ideally there should be a fallback that also works on GNU/Hurd. An approach that passes both in principle is searching for MemTotal in /proc/meminfo. Other unixoid kernels would be nice, but are less important here.
• On Linux, we tend to partition machines into containers. The resources of a container can be partitioned using control groups. For instance setting memory.max on the memory controller of a container cgroup2 would result in the OOM killer to be invoked sooner rather than later.
• It is unclear how this would apply to memory ballooning in virtual machines.

Obviously, this can only be a guess and reality will differ. However, coming up with a guess would allow for more efficient resource consumption and avoiding builds getting killed several hours into them.

The baseline is MemTotal in /proc/meminfo. Can we do better?

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