Keir Fraser wrote:
On 28/7/08 13:21, "Andre Przywara" <andre.przywara@xxxxxxx> wrote:
Mmh, why not check this in in 3.3? I have noticed this problem already a
year ago and was having some other kind of fix for it (which actually
prefered nodes over zones):
http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00831.html
I think this is a somewhat serious issue on NUMA machines, since with
the automatic pinning now active (new in 3.3!) many domains will end up
with remote memory _all the time_. So I think of this as a bugfix.
Actually I have dma_bitsize=30 hardwired in my Grub's menu.lst for some
months now...
Well, fine, but unfortunately the patch breaks ia64
Fixed.
and doesn't even work properly:
- why should NUMA node 0 be the one that overlaps with default DMA memory?
Because that is the most common configuration? Do you know of any
machine where this is not true? I agree that a dual node machine with 2
gig on each node does not need this patch, but NUMA machines tend to
have more memory than this (especially given the current memory costs).
I changed the default DMA_BITSIZE to 30 bits, this seems to be a
reasonable value.
- a 'large' NUMA node 0 will cause dma_bitsize to be set much larger than
it is currently, thus breaking its original intent.
Fixed in the attached patch. It now caps dma_bitsize to at most 1/4 of
node0 memory.
What about using this patch for Xen 3.3 and work out a more general
solution for Xen 3.4?
Signed off by: Andre Przywara <andre.przywara@xxxxxxx>
Based on the patch from: "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>
--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917
----to satisfy European Law for business letters:
AMD Saxony Limited Liability Company & Co. KG,
Wilschdorfer Landstr. 101, 01109 Dresden, Germany
Register Court Dresden: HRA 4896, General Partner authorized
to represent: AMD Saxony LLC (Wilmington, Delaware, US)
General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy
diff -r 37fae02cc335 xen/common/page_alloc.c
--- a/xen/common/page_alloc.c Fri Jul 25 15:03:03 2008 +0100
+++ b/xen/common/page_alloc.c Mon Jul 28 16:02:40 2008 +0200
@@ -583,6 +583,13 @@
init_heap_pages(pfn_dom_zone_type(i), mfn_to_page(i), 1);
}
+ /* Reserve only up to 25% of node0's memory for DMA */
+ i = pfn_dom_zone_type(NODE_DATA(0)->node_spanned_pages / 4)
+ + PAGE_SHIFT;
+ if ( i < dma_bitsize ) dma_bitsize = i;
+
+ ASSERT(dma_bitsize > PAGE_SHIFT + 1);
+
printk("Domain heap initialised: DMA width %u bits\n", dma_bitsize);
}
#undef avail_for_domheap
diff -r 37fae02cc335 xen/include/asm-ia64/config.h
--- a/xen/include/asm-ia64/config.h Fri Jul 25 15:03:03 2008 +0100
+++ b/xen/include/asm-ia64/config.h Mon Jul 28 16:02:40 2008 +0200
@@ -44,7 +44,7 @@
#define CONFIG_IOSAPIC
#define supervisor_mode_kernel (0)
-#define CONFIG_DMA_BITSIZE 32
+#define CONFIG_DMA_BITSIZE 30
#define PADDR_BITS 48
diff -r 37fae02cc335 xen/include/asm-x86/config.h
--- a/xen/include/asm-x86/config.h Fri Jul 25 15:03:03 2008 +0100
+++ b/xen/include/asm-x86/config.h Mon Jul 28 16:02:40 2008 +0200
@@ -97,7 +97,7 @@
/* Primary stack is restricted to 8kB by guard pages. */
#define PRIMARY_STACK_SIZE 8192
-#define CONFIG_DMA_BITSIZE 32
+#define CONFIG_DMA_BITSIZE 30
#define BOOT_TRAMPOLINE 0x8c000
#define bootsym_phys(sym) \
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