The patch titled
zone init check and report unaligned zone boundaries
has been added to the -mm tree. Its filename is
zone-init-check-and-report-unaligned-zone-boundaries.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Andy Whitcroft <apw@xxxxxxxxxxxx>
To summarise the problem, the buddy allocator currently requires that the
boundaries between zones occur at MAX_ORDER boundaries. The specific case
where we were tripping up on this was in x86 with NUMA enabled. There we try
to ensure that each node's stuct pages are in node local memory, in order to
allow them to be virtually mapped we have to reduce the size of ZONE_NORMAL.
Here we are rounding the remap space up to a large page size to allow large
page TLB entries to be used. However, these are smaller than MAX_ORDER. This
can lead to bad buddy merges. With VM_DEBUG enabled we detect the attempts to
merge across this boundary and panic.
We have two basic options we can either apply the appropriate alignment when
we make make the NUMA remap space, or we can 'fix' the assumption in the buddy
allocator. The fix for the buddy allocator involves adding conditionals to
the free fast path and so it seems reasonable to at least favor realigning the
remap space.
Following this email are 3 patches:
zone-init-check-and-report-unaligned-zone-boundaries -- introduces
a zone alignement helper, and uses it to add a check to zone
initialisation for unaligned zone boundaries,
x86-align-highmem-zone-boundaries-with-NUMA -- uses the zone alignment
helper to align the end of ZONE_NORMAL after the remap space has
been reserved, and
zone-allow-unaligned-zone-boundaries -- modifies the buddy allocator
so that we can allow unaligned zone boundaries. A new configuration
option is added to enable this functionality.
The first two are the fixes for alignement in x86, these fix the panics thrown
when VM_DEBUG is enabled.
The last is a patch to support unaligned zone boundaries. As this
(re)introduces a zone check into the free hot path it seems reasonable to only
enable this should it be needed; for example we never need this if we have a
single zone. I have tested the failing system with this patch enabled and it
also fixes the panic. I am inclined to suggest that it be included as it very
clearly documents the alignment requirements for the buddy allocator.
This patch:
We have a number of strict constraints on the layout of struct page's for use
with the buddy allocator. One of which is that zone boundaries must occur at
MAX_ORDER page boundaries. Add a check for this during init.
Signed-off-by: Andy Whitcroft <apw@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/mmzone.h | 5 +++++
mm/page_alloc.c | 4 ++++
2 files changed, 9 insertions(+)
diff -puN include/linux/mmzone.h~zone-init-check-and-report-unaligned-zone-boundaries include/linux/mmzone.h
--- devel/include/linux/mmzone.h~zone-init-check-and-report-unaligned-zone-boundaries 2006-05-11 01:00:06.000000000 -0700
+++ devel-akpm/include/linux/mmzone.h 2006-05-11 01:00:06.000000000 -0700
@@ -398,6 +398,11 @@ static inline int is_dma(struct zone *zo
return zone == zone->zone_pgdat->node_zones + ZONE_DMA;
}
+static inline unsigned long zone_boundary_align_pfn(unsigned long pfn)
+{
+ return pfn & ~((1 << MAX_ORDER) - 1);
+}
+
/* These two functions are used to setup the per zone pages min values */
struct ctl_table;
struct file;
diff -puN mm/page_alloc.c~zone-init-check-and-report-unaligned-zone-boundaries mm/page_alloc.c
--- devel/mm/page_alloc.c~zone-init-check-and-report-unaligned-zone-boundaries 2006-05-11 01:00:06.000000000 -0700
+++ devel-akpm/mm/page_alloc.c 2006-05-11 01:00:06.000000000 -0700
@@ -2351,6 +2351,10 @@ static void __meminit free_area_init_cor
struct zone *zone = pgdat->node_zones + j;
unsigned long size, realsize;
+ if (zone_boundary_align_pfn(zone_start_pfn) != zone_start_pfn)
+ printk(KERN_CRIT "node %d zone %s missaligned "
+ "start pfn\n", nid, zone_names[j]);
+
size = zone_present_pages_in_node(nid, j, zones_size);
realsize = size - zone_absent_pages_in_node(nid, j,
zholes_size);
_
Patches currently in -mm which might be from apw@xxxxxxxxxxxx are
pg_uncached-is-ia64-only.patch
squash-duplicate-page_to_pfn-and-pfn_to_page.patch
introduce-mechanism-for-registering-active-regions-of-memory.patch
have-power-use-add_active_range-and-free_area_init_nodes.patch
have-x86-use-add_active_range-and-free_area_init_nodes.patch
have-x86_64-use-add_active_range-and-free_area_init_nodes.patch
have-ia64-use-add_active_range-and-free_area_init_nodes.patch
zone-init-check-and-report-unaligned-zone-boundaries.patch
x86-align-highmem-zone-boundaries-with-numa.patch
zone-allow-unaligned-zone-boundaries.patch
root-mount-failure-emit-filesystems-attempted.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
