Re: [PATCH] mm: rate-limit allocation failure warnings more aggressively

[David Rientjes <rientjes@google.com>]

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 <hannes@cmpxchg.org>

Acked-by: David Rientjes <rientjes@google.com>

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.