Subject: Re: [5.6.0-rc2-next-20200218/powerpc] Boot failure on POWER9

From: Michal Hocko <[email-masked]>
Date: Wed, 26 Feb 2020 20:01:47 +0100

On Wed 26-02-20 18:44:13, Cristopher Lameter wrote:
> On Wed, 26 Feb 2020, Michal Hocko wrote:
> 
> > Besides that kmalloc_node shouldn't really have an implicit GFP_THISNODE
> > semantic right? At least I do not see anything like that documented
> > anywhere.
> 
> Kmalloc_node does not support memory policies etc. Only kmalloc does.
> kmalloc_node is mostly used by subsystems that have determined the active
> nodes and want a targeted allocation on those nodes.
 
I am sorry but I have hard time to follow your responses here. They open
more questions than they answer for me. The primary point here is that
kmalloc_node on a memory less node blows up and panics the kernel. I
strongly believe this is a bug. We cannot really make all callers of
kmalloc_node and co. to be hotplug aware.

Another question is the semantic of kmalloc_node when the node cannot
satisfy the request. I have always thought that the allocation would
simply fall back to any other node unless __GFP_THISNODE is explicitly
specified.

-- 
Michal Hocko
SUSE Labs