Re: INFO: rcu detected stall in shmem_fault

[Sergey Senozhatsky]

On (10/10/18 13:35), Michal Hocko wrote:
> > Just flooding out of memory messages can trigger RCU stall problems.
> > For example, a severe skbuff_head_cache or kmalloc-512 leak bug is causing
> 
> [...]
> 
> Quite some of them, indeed! I guess we want to rate limit the output.
> What about the following?

A bit unrelated, but while we are at it:

  I like it when we rate-limit printk-s that lookup the system.
But it seems that default rate-limit values are not always good enough,
DEFAULT_RATELIMIT_INTERVAL / DEFAULT_RATELIMIT_BURST can still be too
verbose. For instance, when we have a very slow IPMI emulated serial
console -- e.g. baud rate at 57600. DEFAULT_RATELIMIT_INTERVAL and
DEFAULT_RATELIMIT_BURST can add new OOM headers and backtraces faster
than we evict them.

Does it sound reasonable enough to use larger than default rate-limits
for printk-s in OOM print-outs? OOM reports tend to be somewhat large
and the reported numbers are not always *very* unique.

What do you think?

	-ss