kdump crashkernel=auto not enough memory

Hi,

I use crashkernel=auto for kdump. However OOM killer killed lvm which resulted in a missed vmcore.
My question is if anyone knows how crashkernel=auto works? Is this a bug since the auto doesn't seem to calculate correctly?
The machine have kexec-tools-2.0.0-209.el6.x86_64 and 32GB memory.