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>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/unicore32/mm/init.c b/arch/unicore32/mm/init.c
index de186bde8975..644482882bae 100644
--- a/arch/unicore32/mm/init.c
+++ b/arch/unicore32/mm/init.c
@@ -66,6 +66,9 @@ void show_mem(unsigned int filter)
         printk(KERN_DEFAULT "Mem-info:\n");
         show_free_areas(filter);
 
+        if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
+                return;
+
         for_each_bank(i, mi) {
                 struct membank *bank = &mi->bank[i];
                 unsigned int pfn1, pfn2;