4 ms·

> the amount of RAM all processes need exceeds the amount of memory the system has The word need does the heavy lifting here. Strictly speaking it does not. It

> the amount of RAM all processes need exceeds the amount of memory the system has The word need does the heavy lifting here. Strictly speaking it does not. It CPU only needs a few data and instruction pages at a time to execute code. The former may, the latter frequently will be backed by memory-mapped files. If your program contains huge unicode lookup tables, megabytes of startup code and so on then it is perfectly reasonable to discard those pages. It would be wasteful to keep those resident, especially on memory-constrained devices. Not having swap is not the same as not wanting paging to happen. What the human wants is totally different from what the kernel needs to keep chugging along (at glacial pace). Bridging the gap is what is discussed further downstream in the mailing list linked by the article, and it's only possible based on previous work (PSI) that was added fairly recently.

mrob 7y ago
Why is the kernel deciding if the memory is still needed or not? The kernel can only know how it is used, not why it is used. It can guess the purpose with heuristics, but only the applications know exactly why the memory is used. The correct solution is to disable overcommit, which will force programmers to make use of that superior knowledge to free memory when they no longer need it. We're in this crazy situation because somebody decided to sacrifice reliability to increase efficiency. Efficiency is easier to measure so they got away with it. Fixing the live-lock problem makes things slightly better, but it's not solving the underlying problem. Andries Brouwer's classic comment remains as relevant as ever: https://lwn.net/Articles/104185/ https://lwn.net/Articles/104185/