linux-kernel - Re: [PATCHv2 4.3-rc6] proc: fix convert from oom_score_adj to oom

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Message-ID: <alpine.DEB.2.10.1510261439570.12408@chino.kir.corp.google.com>
Date:	Mon, 26 Oct 2015 14:42:57 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Hongjie Fang (方洪杰) 
	<Hongjie.Fang@...eadtrum.com>
cc:	Michal Hocko <mhocko@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 4.3-rc6] proc: fix convert from oom_score_adj to
 oom_adj

On Thu, 22 Oct 2015, Hongjie Fang (方洪杰) wrote:

> 
> The oom_adj has been replaced by oom_score_adj in kernel,
> but the /proc/pid/oom_adj is provided for legacy purposes.
> When write/read a value into/from /proc/pid/oom_adj,
> there is a transformation between oom_adj and oom_score_adj.
> 
> After writing a new value into /proc/pid/oom_adj, then read it.
> The return value is a different value than you wrote.
> Fix this by adding a adjustment factor.
> 

You're only looking at the output and seeing that it disagrees with what 
was written and ignoring _why_ it disagrees.

It's because, as I already stated, oom_score_adj is the effective tunable 
for oom kill process prioritization and the legacy oom_adj had a different 
scale where a 1:1 mapping is not possible.

All throughout the kernel, we report the effective value.  We accept 
writes and the reads report the effective value.  This is no different.

Nack again.