On Thu 13-06-19 21:55:50, Yafang Shao wrote:
> In dump_oom_summary() oc->constraint is used to show
> oom_constraint_text, but it hasn't been set before.
> So the value of it is always the default value 0.
> We should set it in constrained_alloc().
Thanks for catching that.
> Bellow is the output when memcg oom occurs,
>
> before this patch:
> [ 133.078102] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),
> cpuset=/,mems_allowed=0,oom_memcg=/foo,task_memcg=/foo,task=bash,pid=7997,uid=0
>
> after this patch:
> [ 952.977946] oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),
> cpuset=/,mems_allowed=0,oom_memcg=/foo,task_memcg=/foo,task=bash,pid=13681,uid=0
>
unless I am missing something
Fixes: ef8444ea01d7 ("mm, oom: reorganize the oom report in dump_header")
The patch looks correct but I think it is more complicated than it needs
to be. Can we do the following instead?
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 5a58778c91d4..f719b64741d6 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -987,8 +987,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
/*
* Determines whether the kernel must panic because of the panic_on_oom sysctl.
*/
-static void check_panic_on_oom(struct oom_control *oc,
- enum oom_constraint constraint)
+static void check_panic_on_oom(struct oom_control *oc)
{
if (likely(!sysctl_panic_on_oom))
return;
@@ -998,7 +997,7 @@ static void check_panic_on_oom(struct oom_control *oc,
* does not panic for cpuset, mempolicy, or memcg allocation
* failures.
*/
- if (constraint != CONSTRAINT_NONE)
+ if (oc->constraint != CONSTRAINT_NONE)
return;
}
/* Do not panic for oom kills triggered by sysrq */
@@ -1035,7 +1034,6 @@ EXPORT_SYMBOL_GPL(unregister_oom_notifier);
bool out_of_memory(struct oom_control *oc)
{
unsigned long freed = 0;
- enum oom_constraint constraint = CONSTRAINT_NONE;
if (oom_killer_disabled)
return false;
@@ -1071,10 +1069,10 @@ bool out_of_memory(struct oom_control *oc)
* Check if there were limitations on the allocation (only relevant for
* NUMA and memcg) that may require different handling.
*/
- constraint = constrained_alloc(oc);
- if (constraint != CONSTRAINT_MEMORY_POLICY)
+ oc->constraint = constrained_alloc(oc);
+ if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
oc->nodemask = NULL;
- check_panic_on_oom(oc, constraint);
+ check_panic_on_oom(oc);
if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
I guess the current confusion comes from the fact that we have
constraint both in the oom_control and a local variable so I would
rather remove that. What do you think?
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> mm/oom_kill.c | 35 +++++++++++++++++++++++++----------
> 1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 5a58778..075e5cf 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -261,29 +261,37 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
> struct zone *zone;
> struct zoneref *z;
> enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
> + enum oom_constraint constraint;
> bool cpuset_limited = false;
> int nid;
>
> if (is_memcg_oom(oc)) {
> oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
> - return CONSTRAINT_MEMCG;
> + constraint = CONSTRAINT_MEMCG;
> + goto out;
> }
>
> /* Default to all available memory */
> oc->totalpages = totalram_pages() + total_swap_pages;
>
> - if (!IS_ENABLED(CONFIG_NUMA))
> - return CONSTRAINT_NONE;
> + if (!IS_ENABLED(CONFIG_NUMA)) {
> + constraint = CONSTRAINT_NONE;
> + goto out;
> + }
>
> - if (!oc->zonelist)
> - return CONSTRAINT_NONE;
> + if (!oc->zonelist) {
> + constraint = CONSTRAINT_NONE;
> + goto out;
> + }
> /*
> * Reach here only when __GFP_NOFAIL is used. So, we should avoid
> * to kill current.We have to random task kill in this case.
> * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
> */
> - if (oc->gfp_mask & __GFP_THISNODE)
> - return CONSTRAINT_NONE;
> + if (oc->gfp_mask & __GFP_THISNODE) {
> + constraint = CONSTRAINT_NONE;
> + goto out;
> + }
>
> /*
> * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
> @@ -295,7 +303,8 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
> oc->totalpages = total_swap_pages;
> for_each_node_mask(nid, *oc->nodemask)
> oc->totalpages += node_spanned_pages(nid);
> - return CONSTRAINT_MEMORY_POLICY;
> + constraint = CONSTRAINT_MEMORY_POLICY;
> + goto out;
> }
>
> /* Check this allocation failure is caused by cpuset's wall function */
> @@ -308,9 +317,15 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
> oc->totalpages = total_swap_pages;
> for_each_node_mask(nid, cpuset_current_mems_allowed)
> oc->totalpages += node_spanned_pages(nid);
> - return CONSTRAINT_CPUSET;
> + constraint = CONSTRAINT_CPUSET;
> + goto out;
> }
> - return CONSTRAINT_NONE;
> +
> + constraint = CONSTRAINT_NONE;
> +
> +out:
> + oc->constraint = constraint;
> + return constraint;
> }
>
> static int oom_evaluate_task(struct task_struct *task, void *arg)
> --
> 1.8.3.1
>
--
Michal Hocko
SUSE Labs
