path: root/mm
diff options
authorRuss Anderson <rja@sgi.com>2013-04-29 15:07:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 15:54:35 -0700
commit7c243c7168dcc1bc2081fc0494923cd7cc808fb6 (patch)
tree6d29d01bdf62c64bf430187368bdef21f3919c4a /mm
parentfed5b64a95326697f942f5003c138c7ff3043ef5 (diff)
mm: speedup in __early_pfn_to_nid
When booting on a large memory system, the kernel spends considerable time in memmap_init_zone() setting up memory zones. Analysis shows significant time spent in __early_pfn_to_nid(). The routine memmap_init_zone() checks each PFN to verify the nid is valid. __early_pfn_to_nid() sequentially scans the list of pfn ranges to find the right range and returns the nid. This does not scale well. On a 4 TB (single rack) system there are 308 memory ranges to scan. The higher the PFN the more time spent sequentially spinning through memory ranges. Since memmap_init_zone() increments pfn, it will almost always be looking for the same range as the previous pfn, so check that range first. If it is in the same range, return that nid. If not, scan the list as before. A 4 TB (single rack) UV1 system takes 512 seconds to get through the zone code. This performance optimization reduces the time by 189 seconds, a 36% improvement. A 2 TB (single rack) UV2 system goes from 212.7 seconds to 99.8 seconds, a 112.9 second (53%) reduction. [akpm@linux-foundation.org: make the statics __meminitdata] [akpm@linux-foundation.org: fix comment formatting] [akpm@linux-foundation.org: fix ia64, per yinghai] [akpm@linux-foundation.org: add missing semicolon, per Tony] Signed-off-by: Russ Anderson <rja@sgi.com> Cc: David Rientjes <rientjes@google.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Tested-by: "Luck, Tony" <tony.luck@intel.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Lin Feng <linfeng@cn.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b54c5cbf020..5a234b64f3a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4187,10 +4187,23 @@ int __meminit __early_pfn_to_nid(unsigned long pfn)
unsigned long start_pfn, end_pfn;
int i, nid;
+ /*
+ * NOTE: The following SMP-unsafe globals are only used early in boot
+ * when the kernel is running single-threaded.
+ */
+ static unsigned long __meminitdata last_start_pfn, last_end_pfn;
+ static int __meminitdata last_nid;
+ if (last_start_pfn <= pfn && pfn < last_end_pfn)
+ return last_nid;
for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
- if (start_pfn <= pfn && pfn < end_pfn)
+ if (start_pfn <= pfn && pfn < end_pfn) {
+ last_start_pfn = start_pfn;
+ last_end_pfn = end_pfn;
+ last_nid = nid;
return nid;
+ }
/* This is a memory hole */
return -1;