Commit 4b59e6c4 authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds

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: 's avatarDavid Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: 's avatarMichal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fe0bfaaf
......@@ -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;
......
......@@ -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;
......
......@@ -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;
......
......@@ -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) {
......
......@@ -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;
......
......@@ -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);
......
......@@ -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;
......
......@@ -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
......
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