Messages in this thread | | | Date | Wed, 20 Sep 2017 14:00:23 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH 2/2] mm: oom: show unreclaimable slab info when kernel panic |
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On Thu, 21 Sep 2017, Yang Shi wrote:
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 99736e0..173c423 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -43,6 +43,7 @@ > > #include <asm/tlb.h> > #include "internal.h" > +#include "slab.h" > > #define CREATE_TRACE_POINTS > #include <trace/events/oom.h> > @@ -427,6 +428,14 @@ static void dump_header(struct oom_control *oc, struct task_struct *p) > dump_tasks(oc->memcg, oc->nodemask); > } > > +static void dump_header_with_slabinfo(struct oom_control *oc, struct task_struct *p) > +{ > + dump_header(oc, p); > + > + if (IS_ENABLED(CONFIG_SLABINFO)) > + show_unreclaimable_slab(); > +} > + > /* > * Number of OOM victims in flight > */
I don't think we need a new function for this. Where you want to dump unreclaimable slab before panic, just call a new dump_unreclaimable_slab() function that gets declared in slab.h that is a no-op when CONFIG_SLABINFO is disabled. We just want to do
dump_header(...); dump_unreclaimable_slab(...); panic(...);
> diff --git a/mm/slab.c b/mm/slab.c > index 04dec48..4f4971c 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -4132,6 +4132,7 @@ void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo) > sinfo->shared = cachep->shared; > sinfo->objects_per_slab = cachep->num; > sinfo->cache_order = cachep->gfporder; > + sinfo->reclaim = is_reclaimable(cachep);
We don't need a new field, we already have cachep->flags accessible.
> } > > void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *cachep) > diff --git a/mm/slab.h b/mm/slab.h > index 0733628..2f1ebce 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -186,6 +186,7 @@ struct slabinfo { > unsigned int shared; > unsigned int objects_per_slab; > unsigned int cache_order; > + unsigned int reclaim;
Not needed.
> }; > > void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo); > @@ -352,6 +353,11 @@ static inline void memcg_link_cache(struct kmem_cache *s) > > #endif /* CONFIG_MEMCG && !CONFIG_SLOB */ > > +static inline bool is_reclaimable(struct kmem_cache *s) > +{ > + return (s->flags & SLAB_RECLAIM_ACCOUNT) ? true : false; > +} > +
I don't think we need this.
> static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) > { > struct kmem_cache *cachep; > @@ -504,6 +510,7 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node) > void *memcg_slab_next(struct seq_file *m, void *p, loff_t *pos); > void memcg_slab_stop(struct seq_file *m, void *p); > int memcg_slab_show(struct seq_file *m, void *p); > +void show_unreclaimable_slab(void); > > void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr); > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 904a83b..f2c6200 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -35,6 +35,8 @@ > static DECLARE_WORK(slab_caches_to_rcu_destroy_work, > slab_caches_to_rcu_destroy_workfn); > > +#define K(x) ((x)/1024) > +
I don't think we need this.
> /* > * Set of flags that will prevent slab merging > */ > @@ -1272,6 +1274,35 @@ static int slab_show(struct seq_file *m, void *p) > return 0; > } > > +void show_unreclaimable_slab()
void show_unreclaimable_slab(void)
> +{ > + struct kmem_cache *s = NULL;
No initialization needed.
> + struct slabinfo sinfo; > + > + memset(&sinfo, 0, sizeof(sinfo)); > + > + printk("Unreclaimable slab info:\n"); > + printk("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(s, &slab_caches, list) { > + if (!is_root_cache(s)) > + continue; > +
We need to do the memset() here.
> + get_slabinfo(s, &sinfo); > + > + if (!is_reclaimable(s) && sinfo.num_objs > 0) > + printk("%-17s %10luKB %10luKB\n", cache_name(s), K(sinfo.active_objs * s->size), K(sinfo.num_objs * s->size));
I think you can just check for SLAB_RECLAIM_ACCOUNT here.
Everything in this function should be pr_info().
> + } > +} > +EXPORT_SYMBOL(show_unreclaimable_slab); > +#undef K > + > #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB) > void *memcg_slab_start(struct seq_file *m, loff_t *pos) > { > diff --git a/mm/slub.c b/mm/slub.c > index 163352c..5c17c0a 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5872,6 +5872,7 @@ void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo) > sinfo->num_slabs = nr_slabs; > sinfo->objects_per_slab = oo_objects(s->oo); > sinfo->cache_order = oo_order(s->oo); > + sinfo->reclaim = is_reclaimable(s);
Not needed.
> } > > void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *s)
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