On Sat, Sep 23, 2017, Yang Shi <yan...@alibaba-inc.com> wrote：
>
> Kernel may panic when oom happens without killable process sometimes it
> is caused by huge unreclaimable slabs used by kernel.
>
> Although kdump could help debug such problem, however, kdump is not
> available on all architectures and it might be malfunction sometime.
> And, since kernel already panic it is worthy capturing such information
> in dmesg to aid touble shooting.
......
> +void dump_unreclaimable_slab(void)
> +{
> + struct kmem_cache *s, *s2;
> + struct slabinfo sinfo;
> +
> + pr_info("Unreclaimable slab info:\n");
> + pr_info("Name Used Total\n");
> +
> + /*
> + * Here acquiring slab_mutex is unnecessary since we don't prefer to
> + * get sleep in oom path right before kernel panic, and avoid race
> + * condition.
> + * Since it is already oom, so there should be not any big allocation
> + * which could change the statistics significantly.
> + */
> + list_for_each_entry_safe(s, s2, &slab_caches, list) {
> + if (!is_root_cache(s) || (s->flags & SLAB_RECLAIM_ACCOUNT))
> + continue;
> +
> + memset(&sinfo, 0, sizeof(sinfo));
> + get_slabinfo(s, &sinfo);
> +
> + if (sinfo.num_objs > 0)
> + pr_info("%-17s %10luKB %10luKB\n", cache_name(s),
> + (sinfo.active_objs * s->size) / 1024,
> + (sinfo.num_objs * s->size) / 1024);
> + }
> +}
> +
Seems it's a good feature and patch is fine, maybe modify like below is better.
Change
if (sinfo.num_objs > 0)
to
if (sinfo.num_objs > 0 && sinfo.actives_objs > 0)
