It's worth mentioning that network block devices aren't the only thing with this problem. Network filesystems have it too. (Specifically, any filesystem driver that has to talk to someone over a network in order to write out a dirty page of file data cache).
The article mentions how unimportant the problem is because of the unimportance of swapping to a network block device, but in contrast, buffering writes to a network filesystem is pretty important.
In fact, deadlocks are easy to come by with network filesystems, except that there are arbitrary limits placed on the amount of memory that can be used for file data cache -- in effect, a very large reserve is made for network memory requirements. If the resource inversion could actually be fixed, we could free filesystems to be more self-tuning and make more efficient use of available memory.
Copyright © 2018, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds