Re: [PATCH 3/5] oom: oom-killer don't use proportion of system-ram internally

[CAI Qian <caiqian@redhat.com>]

Hello KOSAKI,

----- Original Message -----
> CAI Qian reported his kernel did hang-up if he ran fork intensive
> workload and then invoke oom-killer.
> 
> The problem is, current oom calculation uses 0-1000 normalized value
> (The unit is a permillage of system-ram). Its low precision make
> a lot of same oom score. IOW, in his case, all processes have smaller
> oom score than 1 and internal calculation round it to 1.
> 
> Thus oom-killer kill ineligible process. This regression is caused by
> commit a63d83f427 (oom: badness heuristic rewrite).
> 
> The solution is, the internal calculation just use number of pages
> instead of permillage of system-ram. And convert it to permillage
> value at displaying time.
> 
> This patch doesn't change any ABI (included /proc/<pid>/oom_score_adj)
> even though current logic has a lot of my dislike thing.
> 
> Reported-by: CAI Qian <caiqian@redhat.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
> fs/proc/base.c | 13 ++++++----
> include/linux/oom.h | 7 +----
> mm/oom_kill.c | 60 +++++++++++++++++++++++++++++++++-----------------
> 3 files changed, 49 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index dfa5327..d6b0424 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -476,14 +476,17 @@ static const struct file_operations
> proc_lstats_operations = {
> 
> static int proc_oom_score(struct task_struct *task, char *buffer)
> {
> - unsigned long points = 0;
> + unsigned long points;
> + unsigned long ratio = 0;
> + unsigned long totalpages = totalram_pages + total_swap_pages + 1;
> 
> read_lock(&tasklist_lock);
> - if (pid_alive(task))
> - points = oom_badness(task, NULL, NULL,
> - totalram_pages + total_swap_pages);
> + if (pid_alive(task)) {
> + points = oom_badness(task, NULL, NULL, totalpages);
> + ratio = points * 1000 / totalpages;
> + }
> read_unlock(&tasklist_lock);
> - return sprintf(buffer, "%lu\n", points);
> + return sprintf(buffer, "%lu\n", ratio);
> }
> 
> struct limit_names {
> diff --git a/include/linux/oom.h b/include/linux/oom.h
> index 5e3aa83..0f5b588 100644
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -40,7 +40,8 @@ enum oom_constraint {
> CONSTRAINT_MEMCG,
> };
> 
> -extern unsigned int oom_badness(struct task_struct *p, struct
> mem_cgroup *mem,
> +/* The badness from the OOM killer */
> +extern unsigned long oom_badness(struct task_struct *p, struct
> mem_cgroup *mem,
> const nodemask_t *nodemask, unsigned long totalpages);
> extern int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t
> gfp_flags);
> extern void clear_zonelist_oom(struct zonelist *zonelist, gfp_t
> gfp_flags);
> @@ -62,10 +63,6 @@ static inline void oom_killer_enable(void)
> oom_killer_disabled = false;
> }
> 
> -/* The badness from the OOM killer */
> -extern unsigned long badness(struct task_struct *p, struct mem_cgroup
> *mem,
> - const nodemask_t *nodemask, unsigned long uptime);
> -
> extern struct task_struct *find_lock_task_mm(struct task_struct *p);
> 
> /* sysctls */
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index e6a6c6f..8bbc3df 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -132,10 +132,12 @@ static bool oom_unkillable_task(struct
> task_struct *p,
> * predictable as possible. The goal is to return the highest value for
> the
> * task consuming the most memory to avoid subsequent oom failures.
> */
> -unsigned int oom_badness(struct task_struct *p, struct mem_cgroup
> *mem,
> +unsigned long oom_badness(struct task_struct *p, struct mem_cgroup
> *mem,
> const nodemask_t *nodemask, unsigned long totalpages)
> {
> - int points;
> + unsigned long points;
> + unsigned long score_adj = 0;
> +
> 
> if (oom_unkillable_task(p, mem, nodemask))
> return 0;
> @@ -160,7 +162,7 @@ unsigned int oom_badness(struct task_struct *p,
> struct mem_cgroup *mem,
> */
> if (p->flags & PF_OOM_ORIGIN) {
> task_unlock(p);
> - return 1000;
> + return ULONG_MAX;
> }
This part failed to apply to the latest git tree so unable to test those
patches this time. Can you fix that?

Thanks,
CAI Qian
> /*
> @@ -176,33 +178,49 @@ unsigned int oom_badness(struct task_struct *p,
> struct mem_cgroup *mem,
> */
> points = get_mm_rss(p->mm) + p->mm->nr_ptes;
> points += get_mm_counter(p->mm, MM_SWAPENTS);
> -
> - points *= 1000;
> - points /= totalpages;
> task_unlock(p);
> 
> /*
> * Root processes get 3% bonus, just like the __vm_enough_memory()
> * implementation used by LSMs.
> + *
> + * XXX: Too large bonus, example, if the system have tera-bytes
> memory..
> */
> - if (has_capability_noaudit(p, CAP_SYS_ADMIN))
> - points -= 30;
> + if (has_capability_noaudit(p, CAP_SYS_ADMIN)) {
> + if (points >= totalpages / 32)
> + points -= totalpages / 32;
> + else
> + points = 0;
> + }
> 
> /*
> * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
> * either completely disable oom killing or always prefer a certain
> * task.
> */
> - points += p->signal->oom_score_adj;
> + if (p->signal->oom_score_adj >= 0) {
> + score_adj = p->signal->oom_score_adj * (totalpages / 1000);
> + if (ULONG_MAX - points >= score_adj)
> + points += score_adj;
> + else
> + points = ULONG_MAX;
> + } else {
> + score_adj = -p->signal->oom_score_adj * (totalpages / 1000);
> + if (points >= score_adj)
> + points -= score_adj;
> + else
> + points = 0;
> + }
> 
> /*
> * Never return 0 for an eligible task that may be killed since it's
> * possible that no single user task uses more than 0.1% of memory and
> * no single admin tasks uses more than 3.0%.
> */
> - if (points <= 0)
> - return 1;
> - return (points < 1000) ? points : 1000;
> + if (!points)
> + points = 1;
> +
> + return points;
> }
> 
> /*
> @@ -274,7 +292,7 @@ static enum oom_constraint
> constrained_alloc(struct zonelist *zonelist,
> *
> * (not docbooked, we don't want this one cluttering up the manual)
> */
> -static struct task_struct *select_bad_process(unsigned int *ppoints,
> +static struct task_struct *select_bad_process(unsigned long *ppoints,
> unsigned long totalpages, struct mem_cgroup *mem,
> const nodemask_t *nodemask)
> {
> @@ -283,7 +301,7 @@ static struct task_struct
> *select_bad_process(unsigned int *ppoints,
> *ppoints = 0;
> 
> do_each_thread_reverse(g, p) {
> - unsigned int points;
> + unsigned long points;
> 
> if (!p->mm)
> continue;
> @@ -314,7 +332,7 @@ static struct task_struct
> *select_bad_process(unsigned int *ppoints,
> */
> if (p == current) {
> chosen = p;
> - *ppoints = 1000;
> + *ppoints = ULONG_MAX;
> } else {
> /*
> * If this task is not being ptraced on exit,
> @@ -445,14 +463,14 @@ static int oom_kill_task(struct task_struct *p,
> struct mem_cgroup *mem)
> #undef K
> 
> static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int
> order,
> - unsigned int points, unsigned long totalpages,
> + unsigned long points, unsigned long totalpages,
> struct mem_cgroup *mem, nodemask_t *nodemask,
> const char *message)
> {
> struct task_struct *victim = p;
> struct task_struct *child;
> struct task_struct *t = p;
> - unsigned int victim_points = 0;
> + unsigned long victim_points = 0;
> 
> if (printk_ratelimit())
> dump_header(p, gfp_mask, order, mem, nodemask);
> @@ -467,7 +485,7 @@ static int oom_kill_process(struct task_struct *p,
> gfp_t gfp_mask, int order,
> }
> 
> task_lock(p);
> - pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
> + pr_err("%s: Kill process %d (%s) points %lu or sacrifice child\n",
> message, task_pid_nr(p), p->comm, points);
> task_unlock(p);
> 
> @@ -479,7 +497,7 @@ static int oom_kill_process(struct task_struct *p,
> gfp_t gfp_mask, int order,
> */
> do {
> list_for_each_entry(child, &t->children, sibling) {
> - unsigned int child_points;
> + unsigned long child_points;
> 
> if (child->mm == p->mm)
> continue;
> @@ -526,7 +544,7 @@ static void check_panic_on_oom(enum oom_constraint
> constraint, gfp_t gfp_mask,
> void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
> {
> unsigned long limit;
> - unsigned int points = 0;
> + unsigned long points = 0;
> struct task_struct *p;
> 
> /*
> @@ -675,7 +693,7 @@ void out_of_memory(struct zonelist *zonelist,
> gfp_t gfp_mask,
> struct task_struct *p;
> unsigned long totalpages;
> unsigned long freed = 0;
> - unsigned int points;
> + unsigned long points;
> enum oom_constraint constraint = CONSTRAINT_NONE;
> int killed = 0;
> 
> --
> 1.7.3.1
> 
> 
> 
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