kdump fails to initialise with `crashkernel=1024M@16M` on some RHEL5 kernels

Solution Unverified - Updated -


On some RHEL5 kernels since RHEL5.5, attempting to use settings of crashkernel=1024M@16M in grub.conf to initialise kdump fails with:

crashkernel reservation failed - memory is in use  
crashkernel reservation failed - memory is in use

However lower values like crashkernel=512M@16M will work fine.


  • Red Hat Enterprise Linux 5
  • kdump/kexec configured to capture vmcore
  • Large memory system
  • Large kdump crashkernel offset

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