On 1/12/21 10:21 AM, Faiyaz Mohammed wrote:
> Reading the sys slab alloc_calls, free_calls returns the available object
> owners, but the size of this file is limited to PAGE_SIZE
> because of the limitation of sysfs attributes, it is returning the
> partial owner info, which is not sufficient to debug/account the slab
> memory and alloc_calls output is not matching with /proc/slabinfo.
>
> To remove the PAGE_SIZE limitation converted the sys slab
> alloc_calls, free_calls to bin attribute.
>
> Signed-off-by: Faiyaz Mohammed <faiyazm@xxxxxxxxxxxxxx>
> ---
> mm/slub.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 47 insertions(+), 14 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index b52384e..8744e5ec 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4710,13 +4710,14 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
> }
>
> static int list_locations(struct kmem_cache *s, char *buf,
> - enum track_item alloc)
> + loff_t offset, enum track_item alloc)
> {
> int len = 0;
> unsigned long i;
> struct loc_track t = { 0, 0, NULL };
> int node;
> struct kmem_cache_node *n;
> + static unsigned int previous_read_count;
Hmm static? What about parallel reads from different files? I guess you'll have
to somehow employ the offset parameter here and it won't be pretty, because you
are still printing free text and not some fixed-size binary chunks where seeking
is simple.
Also it's wasteful to to repeat the data gathering for each pritned page, you'd
need a mechanism that allows holding private data between printing out the
pages. If bin_attribute doesn't have that, you'd need e.g. seq_file which we use
for /proc/pid/(s)maps etc.
> unsigned long *map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
This line doesn't exist since 90e9f6a66c78f in v5.6-rc1, is the patch based on
an old kernel?
> if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
> @@ -4742,11 +4743,9 @@ static int list_locations(struct kmem_cache *s, char *buf,
> spin_unlock_irqrestore(&n->list_lock, flags);
> }
>
> - for (i = 0; i < t.count; i++) {
> + for (i = previous_read_count; i < t.count; i++) {
> struct location *l = &t.loc[i];
>
> - if (len > PAGE_SIZE - KSYM_SYMBOL_LEN - 100)
> - break;
> len += sprintf(buf + len, "%7ld ", l->count);
>
> if (l->addr)
> @@ -4784,12 +4783,20 @@ static int list_locations(struct kmem_cache *s, char *buf,
> nodemask_pr_args(&l->nodes));
>
> len += sprintf(buf + len, "\n");
> +
> + if (len > PAGE_SIZE - KSYM_SYMBOL_LEN - 100) {
> + previous_read_count = i + 1;
> + break;
> + }
> }
>
> + if ((offset != 0) && ((i >= t.count) || (previous_read_count > t.count))) {
> + previous_read_count = 0;
> + len = 0;
> + } else if (!t.count)
> + len += sprintf(buf, "No data\n");
> free_loc_track(&t);
> bitmap_free(map);
> - if (!t.count)
> - len += sprintf(buf, "No data\n");
> return len;
> }
>
> @@ -5180,6 +5187,7 @@ static int any_slab_objects(struct kmem_cache *s)
>
> struct slab_attribute {
> struct attribute attr;
> + struct bin_attribute bin_attr;
> ssize_t (*show)(struct kmem_cache *s, char *buf);
> ssize_t (*store)(struct kmem_cache *s, const char *x, size_t count);
> };
> @@ -5192,6 +5200,12 @@ struct slab_attribute {
> static struct slab_attribute _name##_attr = \
> __ATTR(_name, 0600, _name##_show, _name##_store)
>
> +#define SLAB_BIN_ATTR_RO(_name) \
> + static struct slab_attribute _name##_attr = { \
> + .bin_attr = \
> + __BIN_ATTR_RO(_name, 0) \
> + } \
> +
> static ssize_t slab_size_show(struct kmem_cache *s, char *buf)
> {
> return sprintf(buf, "%u\n", s->size);
> @@ -5535,21 +5549,33 @@ static ssize_t validate_store(struct kmem_cache *s,
> }
> SLAB_ATTR(validate);
>
> -static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)
> +static ssize_t alloc_calls_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr, char *buf,
> + loff_t offset, size_t count)
> {
> + struct kmem_cache *s;
> +
> + s = to_slab(kobj);
> if (!(s->flags & SLAB_STORE_USER))
> return -ENOSYS;
> - return list_locations(s, buf, TRACK_ALLOC);
> +
> + return list_locations(s, buf, offset, TRACK_ALLOC);
> }
> -SLAB_ATTR_RO(alloc_calls);
> +SLAB_BIN_ATTR_RO(alloc_calls);
>
> -static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
> +static ssize_t free_calls_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr, char *buf,
> + loff_t offset, size_t count)
> {
> + struct kmem_cache *s;
> +
> + s = to_slab(kobj);
> if (!(s->flags & SLAB_STORE_USER))
> return -ENOSYS;
> - return list_locations(s, buf, TRACK_FREE);
> +
> + return list_locations(s, buf, offset, TRACK_FREE);
> }
> -SLAB_ATTR_RO(free_calls);
> +SLAB_BIN_ATTR_RO(free_calls);
> #endif /* CONFIG_SLUB_DEBUG */
>
> #ifdef CONFIG_FAILSLAB
> @@ -5694,6 +5720,14 @@ STAT_ATTR(CPU_PARTIAL_NODE, cpu_partial_node);
> STAT_ATTR(CPU_PARTIAL_DRAIN, cpu_partial_drain);
> #endif /* CONFIG_SLUB_STATS */
>
> +
> +static struct bin_attribute *slab_bin_attrs[] = {
> +#ifdef CONFIG_SLUB_DEBUG
> + &alloc_calls_attr.bin_attr,
> + &free_calls_attr.bin_attr,
> +#endif
> +};
> +
> static struct attribute *slab_attrs[] = {
> &slab_size_attr.attr,
> &object_size_attr.attr,
> @@ -5722,8 +5756,6 @@ static struct attribute *slab_attrs[] = {
> &poison_attr.attr,
> &store_user_attr.attr,
> &validate_attr.attr,
> - &alloc_calls_attr.attr,
> - &free_calls_attr.attr,
> #endif
> #ifdef CONFIG_ZONE_DMA
> &cache_dma_attr.attr,
> @@ -5769,6 +5801,7 @@ static struct attribute *slab_attrs[] = {
>
> static const struct attribute_group slab_attr_group = {
> .attrs = slab_attrs,
> + .bin_attrs = slab_bin_attrs,
> };
>
> static ssize_t slab_attr_show(struct kobject *kobj,
>
