From: Michal Hocko <mhocko@kernel.org>
To: Zhaoyang Huang <huangzhaoyang@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1] ringbuffer: Don't choose the process with adj equal OOM_SCORE_ADJ_MIN
Date: Tue, 10 Apr 2018 11:01:28 +0200 [thread overview]
Message-ID: <20180410090128.GY21835@dhcp22.suse.cz> (raw)
In-Reply-To: <CAGWkznEM=AX=3LWDmgyz4GRkWy81TNdFQQXZ7+W4=Ek4ZsnsJw@mail.gmail.com>
On Tue 10-04-18 16:38:32, Zhaoyang Huang wrote:
> On Tue, Apr 10, 2018 at 4:12 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > On Tue 10-04-18 16:04:40, Zhaoyang Huang wrote:
> >> On Tue, Apr 10, 2018 at 3:49 PM, Michal Hocko <mhocko@kernel.org> wrote:
> >> > On Tue 10-04-18 14:39:35, Zhaoyang Huang wrote:
> >> >> On Tue, Apr 10, 2018 at 2:14 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > [...]
> >> >> > OOM_SCORE_ADJ_MIN means "hide the process from the OOM killer completely".
> >> >> > So what exactly do you want to achieve here? Because from the above it
> >> >> > sounds like opposite things. /me confused...
> >> >> >
> >> >> Steve's patch intend to have the process be OOM's victim when it
> >> >> over-allocating pages for ring buffer. I amend a patch over to protect
> >> >> process with OOM_SCORE_ADJ_MIN from doing so. Because it will make
> >> >> such process to be selected by current OOM's way of
> >> >> selecting.(consider OOM_FLAG_ORIGIN first before the adj)
> >> >
> >> > I just wouldn't really care unless there is an existing and reasonable
> >> > usecase for an application which updates the ring buffer size _and_ it
> >> > is OOM disabled at the same time.
> >> There is indeed such kind of test case on my android system, which is
> >> known as CTS and Monkey etc.
> >
> > Does the test simulate a real workload? I mean we have two things here
> >
> > oom disabled task and an updater of the ftrace ring buffer to a
> > potentially large size. The second can be completely isolated to a
> > different context, no? So why do they run in the single user process
> > context?
> ok. I think there are some misunderstandings here. Let me try to
> explain more by my poor English. There is just one thing here. The
> updater is originally a oom disabled task with adj=OOM_SCORE_ADJ_MIN.
> With Steven's patch, it will periodically become a oom killable task
> by calling set_current_oom_origin() for user process which is
> enlarging the ring buffer. What I am doing here is limit the user
> process to the ones that adj > -1000.
I've understood that part. And I am arguing whether this is really such
an important case to play further tricks. Wouldn't it be much simpler to
put the updater out to a separate process? OOM disabled processes
shouldn't really do unexpectedly large allocations. Full stop. Otherwise
you risk a large system disruptions.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-04-10 9:01 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-08 2:16 [PATCH v1] ringbuffer: Don't choose the process with adj equal OOM_SCORE_ADJ_MIN Zhaoyang Huang
2018-04-08 3:48 ` Steven Rostedt
2018-04-08 5:54 ` Zhaoyang Huang
2018-04-08 12:47 ` Steven Rostedt
2018-04-09 0:56 ` Zhaoyang Huang
2018-04-09 13:49 ` Steven Rostedt
2018-04-10 0:32 ` Zhaoyang Huang
2018-04-10 2:32 ` Zhaoyang Huang
2018-04-10 3:12 ` Steven Rostedt
2018-04-10 3:41 ` Zhaoyang Huang
2018-04-10 6:14 ` Michal Hocko
2018-04-10 6:39 ` Zhaoyang Huang
2018-04-10 7:49 ` Michal Hocko
2018-04-10 8:04 ` Zhaoyang Huang
2018-04-10 8:12 ` Michal Hocko
2018-04-10 8:38 ` Zhaoyang Huang
2018-04-10 9:01 ` Michal Hocko [this message]
2018-04-10 9:32 ` Zhaoyang Huang
2018-04-10 9:51 ` Zhaoyang Huang
2018-04-10 10:49 ` Michal Hocko
2018-04-10 12:23 ` Steven Rostedt
2018-04-10 12:27 ` Michal Hocko
2018-04-10 12:36 ` Steven Rostedt
2018-04-10 13:13 ` Steven Rostedt
2018-04-10 13:14 ` Steven Rostedt
2018-04-10 16:45 ` Joel Fernandes
2018-04-10 18:00 ` Steven Rostedt
2018-04-10 18:39 ` Joel Fernandes
2018-04-10 19:05 ` Steven Rostedt
2018-04-11 7:48 ` Zhaoyang Huang
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