Re: 05e0caad3b7bd0d0fbeff980bca22f186241a501 breaks ia64 kdump

[Horms <horms@verge.net.au>]

On Fri, Nov 03, 2006 at 06:06:45PM +0800, Zou Nan hai wrote:
> On Fri, 2006-11-03 at 17:27, Mel Gorman wrote:
> > On Fri, 3 Nov 2006, Zou, Nanhai wrote:
> > 
> > > Hi,
> > > 	This patch should fix the issue.
> > >
> > 
> > It would appear to fix the issue for IA64 but you are blotting over the 
> > issue that the map is reporting a one page hole. On arches with really 
> > adjacent regions that are getting merged, the regions will appear to 
> > overlap by one page. What can happen is something like this
> > 
> > PFN ranges for nodes
> > Node 1: 0 -> 1000
> > Node 0: 1000 -> 2000
> > 
> Hi,
>  But the patch Andy and you are commenting is not my patch...., It was
> in the previous thread. 
> My patch was in the attachment.....
> 
>  Sorry for using outlook to send that patch as attachment, my Linux box
> was not accessable at the time when I was posting the patch.
>  I post the patch again, and copy the discription from my previous mail.
> 
> When ia64 kernel is configured as discontinuous memory model, 
> active_pages are added through efi_memmap_walk(filter_rsvd_memory, count_node_pages). 
> filter_rsvd_memory  will filter out all regions in rsvd_regions include 
> - boot param
> - mem map
> - initrd
> - command line
> - **** kernel code and data ***
> - kernel map built from efi memmap
> - crash kernel reserved region
> So the kernel code and data is excluded even without kdump support,
> check /proc/iomem and dmesg for early_node_data can verify that.
> But magically, the first kernel boots happily without any complain...,
> I guess that is related to the init value in memmap. 
> 
> This patch use another filter to add_acvitive_pages, only exclude crash kernel reserved region if CONFIG_KEXEC is on.

Hi Nan hai,

I can confirm that your patch does indeed resolve the problem that I am
seeint, and it seems to produce PFN ranges that are correct. Though I
must admit I don't entirely follow how skipping the crash-kernel range
in the first kernel effects things in the second kernel.

Also, I am wondering if the following patch, which just 
has filter_rsvd_memory() skip the region matching crashk_res
achives the same as your patch. It does seem to work.


Index: linux-2.6/arch/ia64/kernel/setup.c
=================================--- linux-2.6.orig/arch/ia64/kernel/setup.c	2006-11-06 11:30:56.000000000 +0900
+++ linux-2.6/arch/ia64/kernel/setup.c	2006-11-06 12:07:08.000000000 +0900
@@ -163,6 +163,9 @@
 	func = arg;
 
 	for (i = 0; i < num_rsvd_regions; ++i) {
+		if (rsvd_region[i].start = crashk_res.start &&
+		    rsvd_region[i].end = crashk_res.end)
+			continue;
 		range_start = max(start, prev_start);
 		range_end   = min(end, rsvd_region[i].start);