[patch 10/17] mm/page_alloc.c: ratelimit allocation failure warnings more aggressively

[akpm@linux-foundation.org]

From: Johannes Weiner <hannes@cmpxchg.org>
Subject: mm/page_alloc.c: ratelimit allocation failure warnings more aggressively

While investigating a bug related to higher atomic allocation failures, we
noticed the failure warnings positively drowning the console, and in our
case trigger lockup warnings because of a serial console too slow to
handle all that output.

But even if we had a faster console, it's unclear what additional
information the current level of repetition provides.

Allocation failures happen for three reasons: The machine is OOM, the VM
is failing to handle reasonable requests, or somebody is making
unreasonable requests (and didn't acknowledge their opportunism with
__GFP_NOWARN).  Having the memory dump, a callstack, and the ratelimit
stats on skipped failure warnings should provide enough information to let
users/admins/developers know whether something is wrong and point them in
the right direction for debugging, bpftracing etc.

Limit allocation failure warnings to 1 spew every ten seconds.

Link: http://lkml.kernel.org/r/20191028194906.26899-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/mm/page_alloc.c~mm-rate-limit-allocation-failure-warnings-more-aggressively
+++ a/mm/page_alloc.c
@@ -3728,10 +3728,6 @@ try_this_zone:
 static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
 {
 	unsigned int filter = SHOW_MEM_FILTER_NODES;
-	static DEFINE_RATELIMIT_STATE(show_mem_rs, HZ, 1);
-
-	if (!__ratelimit(&show_mem_rs))
-		return;
 
 	/*
 	 * This documents exceptions given to allocations in certain
@@ -3752,8 +3748,7 @@ void warn_alloc(gfp_t gfp_mask, nodemask
 {
 	struct va_format vaf;
 	va_list args;
-	static DEFINE_RATELIMIT_STATE(nopage_rs, DEFAULT_RATELIMIT_INTERVAL,
-				      DEFAULT_RATELIMIT_BURST);
+	static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
 
 	if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
 		return;
_