[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20100211134343.4886499c.akpm@linux-foundation.org>
Date: Thu, 11 Feb 2010 13:43:43 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Rientjes <rientjes@...gle.com>
Cc: Rik van Riel <riel@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Nick Piggin <npiggin@...e.de>,
Andrea Arcangeli <aarcange@...hat.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Lubos Lunak <l.lunak@...e.cz>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [patch 4/7 -mm] oom: badness heuristic rewrite
On Thu, 11 Feb 2010 01:14:43 -0800 (PST)
David Rientjes <rientjes@...gle.com> wrote:
> On Wed, 10 Feb 2010, Rik van Riel wrote:
>
> > > OOM_ADJUST_MIN and OOM_ADJUST_MAX have been exported to userspace since
> > > 2006 via include/linux/oom.h. This alters their values from -16 to -1000
> > > and from +15 to +1000, respectively.
> >
> > That seems like a bad idea. Google may have the luxury of
> > being able to recompile all its in-house applications, but
> > this will not be true for many other users of /proc/<pid>/oom_adj
> >
>
> Changing any value that may have a tendency to be hardcoded elsewhere is
> always controversial, but I think the nature of /proc/pid/oom_adj allows
> us to do so for two specific reasons:
>
> - hardcoded values tend not the fall within a range, they tend to either
> always prefer a certain task for oom kill first or disable oom killing
> entirely. The current implementation uses this as a bitshift on a
> seemingly unpredictable and unscientific heuristic that is very
> difficult to predict at runtime. This means that fewer and fewer
> applications would hardcode a value of '8', for example, because its
> semantics depends entirely on RAM capacity of the system to begin with
> since badness() scores are only useful when used in comparison with
> other tasks.
You'd be amazed what dumb things applications do. Get thee to
http://google.com/codesearch?hl=en&lr=&q=[^a-z]oom_adj[^a-z]&sbtn=Search
and start reading. All 641 matches ;)
Here's one which which writes -16:
http://google.com/codesearch/p?hl=en#eN5TNOm7KtI/trunk/wlan/vendor/asus/eeepc/init.rc&q=[^a-z]oom_adj[^a-z]&sa=N&cd=70&ct=rc
Let's not change the ABI please.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists