On Fri, 18 Aug 2017, John Stoffel wrote: > Mikulas> The limit can't be changed. I expect that no one will run a system with > Mikulas> such a tight requirements that the memory is used up to the last 2%. > > Mikulas> If the user is near hitting the memory limit, he can just add swap space > Mikulas> to solve the problem instead of tuning dm-crypt. > > My real concern is that we build up too many outstanding BIOs so that > they take along time to process. I'm already seeing some reports > about timeouts after 120 seconds due to stacking of dm-crypt with > other stuff. > > What I'm trying to say is that as memory grows, you need to slow down > the growth of the amount of memory that dm-crypt can allocate. It's > more important to scale by the speed of the IO sub-system than the > size of memory. > > But hey, you really addresed my concern with smaller memory systems > already. > > John This patch doesn't restrict the number of in-flight bios. Lowering the memory limit has no effect on the number of bios being allocated by some other part of the kernel and submitted for dm-crypt. Some times ago I made a patch that limits the number of in-flight bios in device mapper - see this: http://people.redhat.com/~mpatocka/patches/kernel/dm-limit-outstanding-bios/ Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
