[Bug 159356] Re: When DMA is disabled system freeze on high memory usage

The patch was never merged. The big was closed because there was an improvement in 4.17.5, and it seems like many reports like these are just closed, and never fixed. This issue still very much exists in 4.19.
Some observations:
This issue gets more apparent when you have less physical memory (system less likely to unfreeze)
If you have a full swap drive, and full ram, system freezes to it is force rebooted
If your memory is full, occasionally the system will not freezeㅋ
If the system is swapping when not frozen, it writes more to swap then when it is frozen.
If swap is being used, logging in is very slow after waking computer up. (Important processes are being swapped out)
Linux OOM killer is most likely not doing its job.
Windows and MacOS does not freeze when using swap. What is the difference with Linux.

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https://bugs.launchpad.net/bugs/159356

Title:
When DMA is disabled system freeze on high memory usage

Status in linux package in Ubuntu:
Incomplete

Bug description:
I run a batch matlab job server here at my lab, running Dapper 6.06 (for the LTS). One of the users has submitted a very memory-consuming job, which successfully crashes the server. Upon closer inspection, the crash happens like this:
1. I run matlab with the given file (as an ordinary, unpriveleged user)
2. RAM usage quickly fills up
3. Once the RAM meter hits 100%, the system freezes: All SSH connections freeze up, and while switching VTs directly on the machine works, no new processes run - so one can't log in, or do anything if he is logged in. (Sometimes typing doesn't work at all)

Note that the swap - while 7 gigs of it are available - is never used.
(The machine has 7 gigs of RAM as well)

I've tried the same on my Gutsy 32-bit box, and there was no system
freezeup - matlab simply notified that the system was out of memory.
However, it did this once memory was 100% in use - and still, swap
didn't get used at all! (Though it is mounted correctly and shows up
in "top" and "free").

So first thing's first - I'd like to eliminate the crash issue. I
suppose I could switch the server to 32-bit, but I think that would be
a performance loss, considering that it does a lot of heavy
computation. There is no reason, however, that this should happen on a
64-bit machine anyway. Why does it?

WORKAROUND: Enabling DMA in the BIOS

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