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authorDave Hansen <haveblue@us.ibm.com>2005-10-29 18:16:53 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-29 21:40:44 -0700
commitbdc8cb984576ab5b550c8b24c6fa111a873503e3 (patch)
treef94548988874caa10d770e6e65bc50c925abf825 /include/linux/mmzone.h
parent208d54e5513c0c02d85af0990901354c74364d5c (diff)
downloadop-kernel-dev-bdc8cb984576ab5b550c8b24c6fa111a873503e3.zip
op-kernel-dev-bdc8cb984576ab5b550c8b24c6fa111a873503e3.tar.gz
[PATCH] memory hotplug locking: zone span seqlock
See the "fixup bad_range()" patch for more information, but this actually creates a the lock to protect things making assumptions about a zone's size staying constant at runtime. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux/mmzone.h')
-rw-r--r--include/linux/mmzone.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e050d68..f5fa308 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -12,6 +12,7 @@
#include <linux/threads.h>
#include <linux/numa.h>
#include <linux/init.h>
+#include <linux/seqlock.h>
#include <asm/atomic.h>
/* Free memory management - zoned buddy allocator. */
@@ -137,6 +138,10 @@ struct zone {
* free areas of different sizes
*/
spinlock_t lock;
+#ifdef CONFIG_MEMORY_HOTPLUG
+ /* see spanned/present_pages for more description */
+ seqlock_t span_seqlock;
+#endif
struct free_area free_area[MAX_ORDER];
@@ -220,6 +225,16 @@ struct zone {
/* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
unsigned long zone_start_pfn;
+ /*
+ * zone_start_pfn, spanned_pages and present_pages are all
+ * protected by span_seqlock. It is a seqlock because it has
+ * to be read outside of zone->lock, and it is done in the main
+ * allocator path. But, it is written quite infrequently.
+ *
+ * The lock is declared along with zone->lock because it is
+ * frequently read in proximity to zone->lock. It's good to
+ * give them a chance of being in the same cacheline.
+ */
unsigned long spanned_pages; /* total size, including holes */
unsigned long present_pages; /* amount of memory (excluding holes) */
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