linux-kernel - Re: [patch v3 1/3] mm, oom: organize oom context into struct

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Message-Id: <20150714155251.ddb7ef5a54b3b1f49d5fc968@linux-foundation.org>
Date:	Tue, 14 Jul 2015 15:52:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Michal Hocko <mhocko@...e.cz>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch v3 1/3] mm, oom: organize oom context into struct

On Wed, 8 Jul 2015 16:42:42 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote:

> There are essential elements to an oom context that are passed around to
> multiple functions.
> 
> Organize these elements into a new struct, struct oom_control, that
> specifies the context for an oom condition.
> 
> This patch introduces no functional change.
> 
> ...
>
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -12,6 +12,14 @@ struct notifier_block;
>  struct mem_cgroup;
>  struct task_struct;
>  
> +struct oom_control {
> +	struct zonelist *zonelist;
> +	nodemask_t	*nodemask;
> +	gfp_t		gfp_mask;
> +	int		order;
> +	bool		force_kill;
> +};

Some docs would be nice.

gfp_mask and order are what the page-allocating caller originally asked
for, I think?  They haven't been mucked with?

It's somewhat obvious what force_kill does, but why is it provided, why
is it set?  And what does it actually kill?  A process which was
selected based on the other fields...

Also, it's a bit odd that zonelist and nodemask are here.  They're
low-level implementation details whereas the other three fields are
high-level caller control stuff.

Anyway, please have a think about it.  The definition site for a controlling
structure can be a great place to reveal the overall design and operation.
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