[PATCH 0/2] time and space saving patches for large memories

[Cliff Wickman]

From: Cliff Wickman <cpw at sgi.com>

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.