Messages in this thread | | | Date | Mon, 26 Jan 2015 13:11:42 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH 3/3] x86, crash: Allocate enough low-mem when crashkernel=high |
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On Fri, Jan 23, 2015 at 06:02:43PM +0100, Borislav Petkov wrote: > On Tue, Jan 06, 2015 at 03:51:14PM +0100, Joerg Roedel wrote: > > From: Joerg Roedel <jroedel@suse.de> > > > > When the crashkernel is loaded above 4GiB in memory the > > first kernel only allocates 72MiB of low-memory for the DMA > > requirements of the second kernel. On systems with many > > devices this is not enough and causes device driver > > initialization errors and failed crash dumps. Set this > > default value to 256MiB to make sure there is enough memory > > This upper limit of 256 looks arbitrary. Are we going to raise it a > couple of years from now if it becomes insufficient then?
Yes, it is arbitrary. I am open for suggestions on what might be a proper value to satisfy most systems.
> It probably won't be easy but is there some more reliable way to > allocate enough memory for DMA on a say per-system basis or whatever...? > Probably not but let me ask it anyway.
Well, there is no easy way. But we could collect information from the loaded drivers on boot about how many dma-memory they allocate and base our allocation on that. Or we solve it in user-space by some more cleverness in creating the kernel command-line for crashkernel=high.
But besides that, I think the first two patches of this set make sense anyway. I understand that the third one is debatable.
Joerg
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