Hi Don-san, On Wed, 28 Mar 2012 17:22:04 -0400 Don Zickus <dzickus at redhat.com> wrote: > > I was talking to Vivek about kdump memory requirements and he mentioned > that they vary based on how much system memory is used. > > I was interested in knowing why that was and again he mentioned that > makedumpfile needed lots of memory if it was running on a large machine > (for example 1TB of system memory). > > Looking through the makedumpfile README and using what Vivek remembered of > makedumpfile, we gathered that as the number of pages grows, the more > makedumpfile has to temporarily store the information in memory. The > possible reason was to calculate the size of the file before it was copied > to its final destination? makedumpfile uses the system memory of 2nd-kernel for a bitmap if RHEL. The bitmap represents each page of 1st-kernel is excluded or not. So the bitmap size depends on 1st-kernel's system memory. makedumpfile creates a file /tmp/kdump_bitmapXXXXXX as the bitmap, and the file is created on 2nd-kernel's memory if RHEL, because RHEL does not mount a root filesystem when 2nd-kernel is running. > I was curious if that was true and if it was, would it be possible to only > process memory in chunks instead of all at once. > > The idea is that a machine with 4Gigs of memory should consume the same > the amount of kdump runtime memory as a 1TB memory system. > > Just trying to research ways to keep the memory requirements consistent > across all memory ranges. I think the above purpose is good, and I don't have any idea for reducing the bitmap size. And now I am out of makedumpfile development. Kumagai-san is the makedumpfile maintainer now, and he will help you. Thanks Ken'ichi Ohmichi
