Comment 479 for bug 620074

The strange thing about every high throughput io is that *every* byte of memory is used up intil a certain limit. That use of memory will even swap out stuff.

Also looking at especially stress_noswap_nohang.vmstat the behavior mimics this.

1. Place data to be written into memory
2. Write some data to the disk
3. goto 1 if not all allowed memory is used.

Interesting is that "stress -d 1" places data into memory a lot faster than a normal hard disk can handle. So the memory will be filled up eventually (the limit will be reached eventually).

So for me I only have a hanging system when "stress -d 1" writes compete with "swap out" - which is actually caused by "stress -d 1" filling the memory.

So the big question: Why do the kernel allow large data writes to fill up the memory and even swap out stuff just to get data to be written into memory?