On Tue 10-04-18 16:38:32, Zhaoyang Huang wrote: > On Tue, Apr 10, 2018 at 4:12 PM, Michal Hocko <mho...@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 <mho...@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 <mho...@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
