On 01/19/2017 11:57 PM, David Rientjes wrote:
> Commit 82e7d3abec86 ("oom: print nodemask in the oom report") implicitly
> sets the allocation nodemask to cpuset_current_mems_allowed when there is
> no effective mempolicy. cpuset_current_mems_allowed is only effective
> when cpusets are enabled, which is also printed by dump_header(), so
> setting the nodemask to cpuset_current_mems_allowed is redundant and
> prevents debugging issues where ac->nodemask is not set properly in the
> page allocator.
>
> This provides better debugging output since
> cpuset_print_current_mems_allowed() is already provided.
>
> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> mm/oom_kill.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -403,12 +403,14 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
>
> static void dump_header(struct oom_control *oc, struct task_struct *p)
> {
> - nodemask_t *nm = (oc->nodemask) ? oc->nodemask : &cpuset_current_mems_allowed;
> -
> - pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
> - current->comm, oc->gfp_mask, &oc->gfp_mask,
> - nodemask_pr_args(nm), oc->order,
> - current->signal->oom_score_adj);
> + pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=",
> + current->comm, oc->gfp_mask, &oc->gfp_mask);
> + if (oc->nodemask)
> + pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
> + else
> + pr_cont("(null)\n");
> + pr_cont(", order=%d, oom_score_adj=%hd\n",
> + oc->order, current->signal->oom_score_adj);
> if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
> pr_warn("COMPACTION is disabled!!!\n");
>
> @@ -417,7 +419,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
> if (oc->memcg)
> mem_cgroup_print_oom_info(oc->memcg, p);
> else
> - show_mem(SHOW_MEM_FILTER_NODES, nm);
> + show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
> if (sysctl_oom_dump_tasks)
> dump_tasks(oc->memcg, oc->nodemask);
> }
>
Could we simplify both patches with something like this?
Although the sizeof("null") is not the nicest thing, because it relies on knowledge
that pointer() in lib/vsprintf.c uses this string. Maybe Rasmus has some better idea?
Thanks,
Vlastimil
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index f746e44d4046..4add88ef63f0 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -103,7 +103,7 @@ extern nodemask_t _unused_nodemask_arg_;
*
* Can be used to provide arguments for '%*pb[l]' when printing a nodemask.
*/
-#define nodemask_pr_args(maskp) MAX_NUMNODES, (maskp)->bits
+#define nodemask_pr_args(maskp) ((maskp) ? MAX_NUMNODES : (int) sizeof("null")), ((maskp) ? (maskp)->bits : NULL)
/*
* The inline keyword gives the compiler room to decide to inline, or
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