From: Cliff Wickman <cpw@xxxxxxx> Back in early 2014 I submitted several patches for your consideration, most of which concerned saving time and disk space when dumping very large memories. I offer two of them again, as being the most important elements for the practical dumping of very large memories. [PATCH 1/2] use raw i/o and root device to use less memory [PATCH 2/2] exclude page structures of non-dumped pages The second patch has a few dependencies on the first. But they are logically separate. They apply to the 1.5.7 source. As an example of the importance of these two concepts: We dump a 2TB system using crashkernel=450M. Without the patches we write a 3.6G dump in about 12 minutes. With the patches we write a 590M dump in about 4 minutes. And the savings multiply as memory size grows.
