linux-kernel - Re: [patch v2 2/3] mm, oom: organize oom context into struct

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Message-ID: <alpine.DEB.2.10.1507081624440.16585@chino.kir.corp.google.com>
Date:	Wed, 8 Jul 2015 16:28:30 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Michal Hocko <mhocko@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v2 2/3] mm, oom: organize oom context into struct

On Thu, 2 Jul 2015, Michal Hocko wrote:

> On Wed 01-07-15 14:37:14, David Rientjes wrote:
> > The force_kill member of struct oom_control isn't needed if an order of
> > -1 is used instead.  This is the same as order == -1 in
> > struct compact_control which requires full memory compaction.
> > 
> > This patch introduces no functional change.
> 
> But it obscures the code and I really dislike this change as pointed out
> previously.
> 

The oom killer is often called at the end of a very lengthy stack since 
memory allocation itself can be called deep in the stack.  Thus, reducing 
the amount of memory, even for a small lil bool, is helpful.  This is 
especially true when other such structs, struct compact_control, does the 
exact same thing by using order == -1 to mean explicit compaction.

I'm personally tired of fixing stack overflows and you're arguing against 
"obscurity" that even occurs in other parts of the mm code.  
oc->force_kill has no reason to exist, and thus it's removed in this patch 
and for good reason.
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