On Tue, 3 Oct 2006, Benjamin Herrenschmidt wrote:
On Thu, 2006-09-14 at 19:11 +0100, Mel Gorman wrote:
On Thu, 14 Sep 2006, Judith Lebzelter wrote:
For ppc in our cross-compile build farm (PLM), there is an error
compiling file ppc/mm/init.c:
CC arch/ppc/mm/init.o
CC arch/powerpc/kernel/init_task.o
arch/ppc/mm/init.c: In function 'paging_init':
arch/ppc/mm/init.c:381: error: subscripted value is neither array nor pointer
arch/ppc/mm/init.c:383: warning: passing argument 1 of '/' makes pointer from integer without a cast
make[1]: [arch/ppc/mm/init.o] Error 1 (ignored)
This is caused by an error/oversight in file
'have-power-use-add_active_range-and-free_area_init_nodes.patch'
Here is a patch to fix that patch.
Looks good. Thanks
Acked-by: Mel Gorman <[email protected]>
Note that the whole ppc patch here seems broken. Sorry for not jumping
earlier, I've been swamped with other things.
First, why the heck do you use indices 0 and 1 explicitely rather than
the symbolic constants ?
Because in the -mm kernel the patches were rolled against, ZONE_DMA was
optional and MAX_NR_ZONES could change which led to this confusion. It is
wrong and thanks for catching it. However, this is a a fairly small part
of the whole patch, is it an exaggeration to call the whole patch broken?
On a semi-related (but not very important) note, why does PPC use ZONE_DMA
as it's lowest zone and not ZONE_NORMAL? I currently view zones as
meaning;
ZONE_DMA - The physical range of memory usable by a subset of devices
available on the target platform (usually considered to be ISA
devices). It is mapped into the kernel
virtual address space
ZONE_DMA32 - The physical range of memory usable by 32 bit devices on 64
bit platforms. It is mapped into the kernel virtual address space
ZONE_NORMAL - The physical range of memory excluding the lower
zones directly mapped into the kernel virtual address space.
ZONE_HIGHMEM - The higher physical address spaces not permanently mapped
into the kernel virtual address space
This is not 100% bullet-proof definition. For example, memmap can be
allocated from highmem and placed in the kernel virtual address space. But
by the definitions above, ppc would have no ZONE_DMA, only ZONE_NORMAL and
ZONE_HIGHMEM. Was ZONE_DMA used for any particular reason?
ppc doesn't have a ZONE_NORMAL, so we should be
filling ZONE_DMA and ZONE_HIGHMEM but you end up filling ZONE_DMA and
ZONE_NORMAL and leave ZONE_HIGHMEM alone. Also, you leave other entries
filled with crap (the array isn't initialized) which cause some strange
display of the PFN list, if not worse problems later, I don't know for
sure at this stage.
By the PFN list, I assume you mean the dmesg entry that starts with "Zone
PFN ranges:". If that is messed up, it is bad, but it should still boot
albeit with memory in the wrong zones.
I've about to run some tests with this patch.
I made a minor comment on your patch below.
Looks like we need give a
closer look at those patches, in case that breakage appears on other
archs as well (or similar).
I looked through the other patches for similar breakage. On x86,
max_zone_pfns is initialised as;
# x86 init
+ unsigned long max_zone_pfns[MAX_NR_ZONES] = {
+ virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT,
+ max_low_pfn,
+ highend_pfn
+ };
as it does not have ZONE_DMA32, I believe it's ok. On x86_64, I used
# x86_64 init
+ unsigned long max_zone_pfns[MAX_NR_ZONES] = {MAX_DMA_PFN,
+ MAX_DMA32_PFN,
+ end_pfn};
This should be ok because x86_64 uses ZONE_NORMAL as the highest zone.
On ia64, there is
# ia64
+ max_zone_pfns[ZONE_DMA] = max_dma;
+ max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
That should also be ok because it doesn't use HIGHMEM.
How do they look to you?
---
New zone initialisation on powerpc is broken, especially with
CONFIG_HIGHMEM, this fixes it by initializing the array to 0 and filling
up the right entries.
Signed-off-by: Benjamin Herrenschmidt <[email protected]>
Index: linux-work/arch/powerpc/mm/mem.c
===================================================================
--- linux-work.orig/arch/powerpc/mm/mem.c 2006-10-03 12:41:03.000000000 +1000
+++ linux-work/arch/powerpc/mm/mem.c 2006-10-03 14:08:30.000000000 +1000
@@ -307,11 +307,12 @@ void __init paging_init(void)
top_of_ram, total_ram);
printk(KERN_DEBUG "Memory hole size: %ldMB\n",
(top_of_ram - total_ram) >> 20);
+ memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
#ifdef CONFIG_HIGHMEM
- max_zone_pfns[0] = total_lowmem >> PAGE_SHIFT;
- max_zone_pfns[1] = top_of_ram >> PAGE_SHIFT;
+ max_zone_pfns[ZONE_DMA] = total_lowmem >> PAGE_SHIFT;
Add
max_zone_pfns[ZONE_NORMAL] = total_lowmem >> PAGE_SHIFT;
The effect will be that ZONE_NORMAL will be initialised as empty.
+ max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
#else
- max_zone_pfns[0] = top_of_ram >> PAGE_SHIFT;
+ max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
#endif
free_area_init_nodes(max_zone_pfns);
}
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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