Comment 45 for bug 246413

a simplier workarround not using LVM or Raid0 is just to create multiple encrypted partitions, each one will run a single kcryptd, but you can isolate the i/o demanding volumes, like the swap or a partition to hold virtual machine disk images

the downside is you need to enter your password multiple times at boot...
somebody said that if you create them at install with the alternate disk you can just use one password, but i lost the reference

at the linux irc somebody suggested the recommended number of partitions is your number of cpu cores + 1

i'm running two partitions on a netbook now to isolate my virtual machine and it seems to work nice, sometimes the computer become slow, but it is not freezing, my VM is not saturating the kcryptd bottleneck anymore, it has its own bottleneck to deal with :P

simplier and more flexible than the raid0 hack, well...