On Thu, 21 Dec 2023, Ruipeng Qi wrote:
> From: qiruipeng <qiruipeng@xxxxxxxxxxx>
>
> Osdump is interested in data stored within slab subsystem. Add full list
> back into corresponding struct, and record full list within respective
> functions instead of enabling SLUB_DEBUG directly, which will intruduce
> sensible overhead.
>
> Signed-off-by: qiruipeng <qiruipeng@xxxxxxxxxxx>
Hi Ruipeng, please make sure to send your patch sets as a single email
thread (all patches 1-7 should be a reply to your 0/7 cover letter).
There is some other feedback on previous patches in this series which
refers to alternatives, so I think the cover letter to the patch series
will need to spell out why we need a brand new solution to this.
That said, from the slab perspective, this is basically splitting out a
part of SLUB_DEBUG into a single feature. Likely best to propose it as a
feature that SLUB_DEBUG would then directly enable itself rather than
duplicating code in definitions.
That is, assuming the question about why we need a new solution for this
can be resolved in the cover letter of a v2.
> ---
> mm/slab.h | 2 ++
> mm/slub.c | 38 +++++++++++++++++++++++++++++++++++++-
> 2 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 3d07fb428393..a42a54c9c5de 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -799,6 +799,8 @@ struct kmem_cache_node {
> atomic_long_t nr_slabs;
> atomic_long_t total_objects;
> struct list_head full;
> +#elif defined(CONFIG_OS_MINIDUMP)
> + struct list_head full;
> #endif
> #endif
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 63d281dfacdb..1a496ec945b6 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1730,10 +1730,26 @@ static inline int check_object(struct kmem_cache *s, struct slab *slab,
> static inline depot_stack_handle_t set_track_prepare(void) { return 0; }
> static inline void set_track(struct kmem_cache *s, void *object,
> enum track_item alloc, unsigned long addr) {}
> +#ifndef CONFIG_OS_MINIDUMP
> static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n,
> struct slab *slab) {}
> static inline void remove_full(struct kmem_cache *s, struct kmem_cache_node *n,
> struct slab *slab) {}
> +#else
> +static inline void add_full(struct kmem_cache *s,
> + struct kmem_cache_node *n, struct slab *slab)
> +{
> + lockdep_assert_held(&n->list_lock);
> + list_add(&slab->slab_list, &n->full);
> +}
> +
> +static inline void remove_full(struct kmem_cache *s, struct kmem_cache_node *n, struct slab *slab)
> +{
> + lockdep_assert_held(&n->list_lock);
> + list_del(&slab->slab_list);
> +}
> +#endif
> +
> slab_flags_t kmem_cache_flags(unsigned int object_size,
> slab_flags_t flags, const char *name)
> {
> @@ -2570,6 +2586,14 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab,
> spin_lock_irqsave(&n->list_lock, flags);
> } else {
> mode = M_FULL_NOLIST;
> +#ifdef CONFIG_OS_MINIDUMP
> + /*
> + * Taking the spinlock removes the possibility that
> + * acquire_slab() will see a slab that is frozen
> + */
> + spin_lock_irqsave(&n->list_lock, flags);
> +
> +#endif
> }
>
>
> @@ -2577,7 +2601,11 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab,
> old.freelist, old.counters,
> new.freelist, new.counters,
> "unfreezing slab")) {
> +#ifndef CONFIG_OS_MINIDUMP
> if (mode == M_PARTIAL)
> +#else
> + if (mode != M_FREE)
> +#endif
> spin_unlock_irqrestore(&n->list_lock, flags);
> goto redo;
> }
> @@ -2592,6 +2620,10 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab,
> discard_slab(s, slab);
> stat(s, FREE_SLAB);
> } else if (mode == M_FULL_NOLIST) {
> +#ifdef CONFIG_OS_MINIDUMP
> + add_full(s, n, slab);
> + spin_unlock_irqrestore(&n->list_lock, flags);
> +#endif
> stat(s, DEACTIVATE_FULL);
> }
> }
> @@ -4202,6 +4234,9 @@ init_kmem_cache_node(struct kmem_cache_node *n)
> atomic_long_set(&n->nr_slabs, 0);
> atomic_long_set(&n->total_objects, 0);
> INIT_LIST_HEAD(&n->full);
> +#elif defined(CONFIG_OS_MINIDUMP)
> + INIT_LIST_HEAD(&n->full);
> +
> #endif
> }
>
> @@ -5009,7 +5044,8 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
> list_for_each_entry(p, &n->partial, slab_list)
> p->slab_cache = s;
>
> -#ifdef CONFIG_SLUB_DEBUG
> +#if defined(CONFIG_SLUB_DEBUG) || \
> + defined(CONFIG_OS_MINIDUMP)
> list_for_each_entry(p, &n->full, slab_list)
> p->slab_cache = s;
> #endif
> --
> 2.17.1
>
>
