linux-kernel - Re: [PATCH 1/5] staging: android: lowmemorykiller: Add config option to support oom

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Message-ID: <CAMP5XgemB4AdKEY4HFLwupo1CGv89hbmB+HUYYN8qdQRYCTdHg@mail.gmail.com>
Date:	Wed, 27 Feb 2013 15:47:17 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/5] staging: android: lowmemorykiller: Add config option
 to support oom_adj values

On Wed, Feb 27, 2013 at 3:12 PM, David Rientjes <rientjes@...gle.com> wrote:
> On Wed, 27 Feb 2013, Arve Hjønnevåg wrote:
>
>> > Umm, writes to /proc/pid/oom_adj already are converted to the
>> > /proc/pid/oom_score_adj scale linearly.  Heavy NACK to this patch since
>> > oom_adj is completely deprecated.
>>
>> I know it is deprecated, but your change, staging: android,
>> lowmemorykiller: convert to use oom_score_adj, broke existing
>> user-space code that still write to /proc/pid/oom_adj. This option
>> lets you build a kernel that supports our user-space code until that
>> user-space has been converted to use /proc/pid/oom_score_adj.
>>
>
> As stated, writes to /proc/pid/oom_adj already are converted to a linear
> scale and stored in /proc/pid/oom_score_adj.  This is done with
>
>         oom_adj == 15   ->      oom_score_adj = 1000
>         oom_adj != 15   ->      oom_score_adj = (oom_adj * -1000) / -17
>
> since the maximum oom_score_adj is 1000 and the minimum oom_adj is -17.
>
> How does this not work as needed?

Because, without this patch, the values written to
/sys/module/lowmemorykiller/parameters/adj do not get adjusted and
therefore do not match the correct processes.

-- 
Arve Hjønnevåg
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