[PATCH] x86_64: Tell VM about holes in nodes

Some nodes can have large holes on x86-64.

This fixes problems with the VM allowing too many dirty pages because it
overestimates the number of available RAM in a node.  In extreme cases you
can end up with all RAM filled with dirty pages which can lead to deadlocks
and other nasty behaviour.

This patch just tells the VM about the known holes from e820.  Reserved
(like the kernel text or mem_map) is still not taken into account, but that
should be only a few percent error now.

Small detail is that the flat setup uses the NUMA free_area_init_node() now
too because it offers more flexibility.

(akpm: lotsa thanks to Martin for working this problem out)

Cc: Martin Bligh <mbligh@mbligh.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-x86_64/e820.h b/include/asm-x86_64/e820.h
index 8e94edf0b984..e682edc24a68 100644
--- a/include/asm-x86_64/e820.h
+++ b/include/asm-x86_64/e820.h
@@ -51,6 +51,8 @@ extern int e820_mapped(unsigned long start, unsigned long end, unsigned type);
 
 extern void e820_bootmem_free(pg_data_t *pgdat, unsigned long start,unsigned long end);
 extern void e820_setup_gap(void);
+extern unsigned long e820_hole_size(unsigned long start_pfn,
+                                    unsigned long end_pfn);
 
 extern void __init parse_memopt(char *p, char **end);