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 <[email protected]> Cc: Mel Gorman <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Dave Hansen <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
zubinmehta · Apr 29, 2013 · 4b59e6c · 4b59e6c
1 parent fe0bfaa
commit 4b59e6c
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Showing 8 changed files with 24 additions and 1 deletion.
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
@@ -99,6 +99,9 @@ void show_mem(unsigned int filter)
 	printk("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;

diff --git 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
@@ -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;

diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
@@ -697,6 +697,8 @@ void show_mem(unsigned int filter)
 
 	printk(KERN_INFO "Mem-info:\n");
 	show_free_areas(filter);
+	if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
+		return;
 #ifndef CONFIG_DISCONTIGMEM
 	i = max_mapnr;
 	while (i-- > 0) {

diff --git 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;

diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -899,7 +899,8 @@ extern void pagefault_out_of_memory(void);
  * Flags passed to show_mem() and show_free_areas() to suppress output in
  * various contexts.
  */
-#define SHOW_MEM_FILTER_NODES	(0x0001u)	/* filter disallowed nodes */
+#define SHOW_MEM_FILTER_NODES		(0x0001u)	/* disallowed nodes */
+#define SHOW_MEM_FILTER_PAGE_COUNT	(0x0002u)	/* page type count */
 
 extern void show_free_areas(unsigned int flags);
 extern bool skip_free_areas_node(unsigned int flags, int nid);

diff --git a/lib/show_mem.c b/lib/show_mem.c
@@ -18,6 +18,9 @@ void show_mem(unsigned int filter)
 	printk("Mem-Info:\n");
 	show_free_areas(filter);
 
+	if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
+		return;
+
 	for_each_online_pgdat(pgdat) {
 		unsigned long i, flags;
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
@@ -2002,6 +2002,13 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...)
 	    debug_guardpage_minorder() > 0)
 		return;
 
+	/*
+	 * Walking all memory to count page types is very expensive and should
+	 * be inhibited in non-blockable contexts.
+	 */
+	if (!(gfp_mask & __GFP_WAIT))
+		filter |= SHOW_MEM_FILTER_PAGE_COUNT;
+
 	/*
 	 * This documents exceptions given to allocations in certain
 	 * contexts that are allowed to allocate outside current's set