>>>>> "Mikulas" == Mikulas Patocka <mpatocka@xxxxxxxxxx> writes: Mikulas> 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 Mikulas> This patch doesn't restrict the number of in-flight bios. Lowering the Mikulas> memory limit has no effect on the number of bios being allocated by some Mikulas> other part of the kernel and submitted for dm-crypt. Good to know. Mikulas> Some times ago I made a patch that limits the number of in-flight bios in Mikulas> device mapper - see this: Mikulas> http://people.redhat.com/~mpatocka/patches/kernel/dm-limit-outstanding-bios/ Interesting. I'll try to find some time to look this over. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
