mm, show_mem: suppress page counts in non-blockable contexts

On large systems with a lot of memory, walking all RAM to determine page
types may take a half second or even more.

In non-blockable contexts, the page allocator will emit a page allocation
failure warning unless __GFP_NOWARN is specified.  In such contexts, irqs
are typically disabled and such a lengthy delay may even result in NMI
watchdog timeouts.

To fix this, suppress the page walk in such contexts when printing the
page allocation failure warning.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 0 deletions

diff --git a/arch/ia64/mm/contig.c b/arch/ia64/mm/contig.c
index 80dab509dfb0..67c59ebec899 100644
--- a/arch/ia64/mm/contig.c
+++ b/arch/ia64/mm/contig.c
@@ -47,6 +47,8 @@ void show_mem(unsigned int filter)
         printk(KERN_INFO "Mem-info:\n");
         show_free_areas(filter);
         printk(KERN_INFO "Node memory in pages:\n");
+        if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
+                return;
         for_each_online_pgdat(pgdat) {
                 unsigned long present;
                 unsigned long flags;
diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
index c2e955ee79a8..a57436e5d405 100644
--- a/arch/ia64/mm/discontig.c
+++ b/arch/ia64/mm/discontig.c
@@ -623,6 +623,8 @@ void show_mem(unsigned int filter)
 
         printk(KERN_INFO "Mem-info:\n");
         show_free_areas(filter);
+        if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
+                return;
         printk(KERN_INFO "Node memory in pages:\n");
         for_each_online_pgdat(pgdat) {
                 unsigned long present;