On Tue, Apr 10, 2018 at 2:14 PM, Michal Hocko <mho...@kernel.org> wrote:
> On Tue 10-04-18 11:41:44, Zhaoyang Huang wrote:
>> On Tue, Apr 10, 2018 at 11:12 AM, Steven Rostedt <rost...@goodmis.org> wrote:
>> > On Tue, 10 Apr 2018 10:32:36 +0800
>> > Zhaoyang Huang <huangzhaoy...@gmail.com> wrote:
>> >
>> >> For bellowing scenario, process A have no intension to exhaust the
>> >> memory, but will be likely to be selected by OOM for we set
>> >> OOM_CORE_ADJ_MIN for it.
>> >> process A(-1000) process B
>> >>
>> >> i = si_mem_available();
>> >> if (i < nr_pages)
>> >> return -ENOMEM;
>> >> schedule
>> >> --------------->
>> >> allocate huge memory
>> >> <-------------
>> >> if (user_thread)
>> >> set_current_oom_origin();
>> >>
>> >> for (i = 0; i < nr_pages; i++) {
>> >> bpage = kzalloc_node
>> >
>> > Is this really an issue though?
>> >
>> > Seriously, do you think you will ever hit this?
>> >
>> > How often do you increase the size of the ftrace ring buffer? For this
>> > to be an issue, the system has to trigger an OOM at the exact moment
>> > you decide to increase the size of the ring buffer. That would be an
>> > impressive attack, with little to gain.
>> >
>> > Ask the memory management people. If they think this could be a
>> > problem, then I'll be happy to take your patch.
>> >
>> > -- Steve
>> add Michael for review.
>> Hi Michael,
>> I would like suggest Steve NOT to set OOM_CORE_ADJ_MIN for the process
>> with adj = -1000 when setting the user space process as potential
>> victim of OOM.
>
> 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...
>
> --
> Michal Hocko
> SUSE Labs
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)
