linux-kernel - RE: [PATCH] mm, oom: normalize the adj to ensure oom

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Message-ID: <alpine.DEB.2.02.1403041400020.5421@chino.kir.corp.google.com>
Date:	Tue, 4 Mar 2014 14:05:42 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	"He, Bo" <bo.he@...el.com>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"oleg@...hat.com" <oleg@...hat.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"Zhang, Yanmin" <yanmin.zhang@...el.com>,
	"yanmin_zhang@...el.linux.com" <yanmin_zhang@...el.linux.com>,
	"Wang, Biao" <biao.wang@...el.com>
Subject: RE: [PATCH]  mm, oom: normalize the adj to ensure oom_badness return
 a positive number

On Tue, 4 Mar 2014, He, Bo wrote:

> Sorry, the title is confusing. Change it to: mm, oom: normalize the adj to ensure oom_badness returns a positive number

There's something seriously wrong with your email client, it's not 
replying correctly to threads so this appears as a completely new thread.  
Meanwhile, your patch was completely whitespace damaged.  Please read 
Documentation/email-clients.txt.

> We are enabling android mobiles. When running stress memory test, there is a bad issue. Some critical processes such as Healthd and watchdogd are killed, while some other processes are still alive.
> OOM should kill the tasks whose oom_score are biggest. Many processes use a minus oom_score_adj. oom_badness returns 1 for all of them and their oom_score are all 0.
> 

No, you're confusing two different things.  A negative 
/proc/pid/oom_score_adj discounts a process's memory usage in comparison 
to other processes.  If this value discounts all memory usage for every 
process, then your setting of /proc/pid/oom_score_adj is wrong.

oom_badness() returns 1 so that the oom killer may still kill these 
processes, the /proc/pid/oom_score is irrelevant to this (and the only 
reason it appears as 0 is because it already normalizes by multiplying by 
1000 / totalpages).

> The patch tries to convert the minus oom_score_adj to a positive number when calculating oom_score. oom_score can keep right process priority sequence.
> 

Nack, this patch is completely disregarding the value specified by the 
user for /proc/pid/oom_score_adj.  Your userspace should be using 
/proc/pid/oom_score_adj, not /proc/pid/oom_adj. 
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