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.
Signed-off-by: Johannes Weiner <[email protected]>
---
mm/page_alloc.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 791c018314b3..f412b17b5d59 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3720,10 +3720,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
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
@@ -3744,8 +3740,7 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
{
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;
--
2.23.0
On Mon, 28 Oct 2019, Johannes Weiner wrote:
> 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.
>
> Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: David Rientjes <[email protected]>
It feels like the vmalloc warnings should be treated with their own
ratelimit (pass a struct ratelimit_state * to warn_alloc()) but that's
outside the scope of this particular change.