On Wed 15-01-14 23:46:44, David Rientjes wrote:
> When two threads have the same badness score, it's preferable to kill the
> thread group leader so that the actual process name is printed to the
> kernel log rather than the thread group name which may be shared amongst
> several processes.
I am not sure I understand this. Is this about ->comm? If yes then why
couldn't the group leader do PR_SET_NAME?
> This was the behavior when select_bad_process() used to do
> for_each_process(), but it now iterates threads instead and leads to
> ambiguity.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> v2: fixes missing get_task_struct() found by Johannes.
>
> mm/memcontrol.c | 19 ++++++++++++-------
> mm/oom_kill.c | 12 ++++++++----
> 2 files changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a815686..d69c4b3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1841,13 +1841,18 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
> break;
> };
> points = oom_badness(task, memcg, NULL, totalpages);
> - if (points > chosen_points) {
> - if (chosen)
> - put_task_struct(chosen);
> - chosen = task;
> - chosen_points = points;
> - get_task_struct(chosen);
> - }
> + if (points < chosen_points)
> + continue;
> + /* Prefer thread group leaders for display purposes */
> + if (points == chosen_points &&
> + thread_group_leader(chosen))
> + continue;
> +
> + if (chosen)
> + put_task_struct(chosen);
> + chosen = task;
> + chosen_points = points;
> + get_task_struct(chosen);
> }
> css_task_iter_end(&it);
> }
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 054ff47..1dca3d8 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -327,10 +327,14 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
> break;
> };
> points = oom_badness(p, NULL, nodemask, totalpages);
> - if (points > chosen_points) {
> - chosen = p;
> - chosen_points = points;
> - }
> + if (points < chosen_points)
> + continue;
> + /* Prefer thread group leaders for display purposes */
> + if (points == chosen_points && thread_group_leader(chosen))
> + continue;
> +
> + chosen = p;
> + chosen_points = points;
> }
> if (chosen)
> get_task_struct(chosen);
--
Michal Hocko
SUSE Labs
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