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Subject: Re: [PATCH] mm: slub: move sysfs slab alloc/free interfaces to
 debugfs
To:     cl@linux.com, penberg@kernel.org, rientjes@google.com,
        iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <1617711959-11146-1-git-send-email-faiyazm@codeaurora.org>
From:   Faiyaz Mohammed <faiyazm@codeaurora.org>
Message-ID: <fdf23581-a5c2-c7ae-c84c-5d8ef82a6c5e@codeaurora.org>
Date:   Tue, 6 Apr 2021 17:58:32 +0530
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Please ignore this patch!

Thanks and regards,
Mohammed Faiyaz.

On 4/6/2021 5:55 PM, Faiyaz Mohammed wrote:
> alloc_calls and free_calls implementation in sysfs have two issues,
> one is PAGE_SIZE limitiation of sysfs and other is it does not adhere
> to "one value per file" rule.
> 
> To overcome this issues, move the alloc_calls and free_calls implemeation
> to debugfs.
> 
> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
> ---
>  mm/slub.c | 518 ++++++++++++++++++++++++++++++++++----------------------------
>  1 file changed, 286 insertions(+), 232 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 3021ce9..4d20ee0 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -36,6 +36,7 @@
>  #include <linux/memcontrol.h>
>  #include <linux/random.h>
>  
> +#include <linux/debugfs.h>
>  #include <trace/events/kmem.h>
>  
>  #include "internal.h"
> @@ -225,6 +226,12 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
>  							{ return 0; }
>  #endif
>  
> +#ifdef CONFIG_DEBUG_FS
> +static void debugfs_slab_add(struct kmem_cache *);
> +#else
> +static inline void debugfs_slab_add(struct kmem_cache *) { }
> +#endif
> +
>  static inline void stat(const struct kmem_cache *s, enum stat_item si)
>  {
>  #ifdef CONFIG_SLUB_STATS
> @@ -4542,6 +4549,8 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
>  	if (err)
>  		__kmem_cache_release(s);
>  
> +	debugfs_slab_add(s);
> +
>  	return err;
>  }
>  
> @@ -4682,221 +4691,6 @@ static long validate_slab_cache(struct kmem_cache *s)
>  
>  	return count;
>  }
> -/*
> - * Generate lists of code addresses where slabcache objects are allocated
> - * and freed.
> - */
> -
> -struct location {
> -	unsigned long count;
> -	unsigned long addr;
> -	long long sum_time;
> -	long min_time;
> -	long max_time;
> -	long min_pid;
> -	long max_pid;
> -	DECLARE_BITMAP(cpus, NR_CPUS);
> -	nodemask_t nodes;
> -};
> -
> -struct loc_track {
> -	unsigned long max;
> -	unsigned long count;
> -	struct location *loc;
> -};
> -
> -static void free_loc_track(struct loc_track *t)
> -{
> -	if (t->max)
> -		free_pages((unsigned long)t->loc,
> -			get_order(sizeof(struct location) * t->max));
> -}
> -
> -static int alloc_loc_track(struct loc_track *t, unsigned long max, gfp_t flags)
> -{
> -	struct location *l;
> -	int order;
> -
> -	order = get_order(sizeof(struct location) * max);
> -
> -	l = (void *)__get_free_pages(flags, order);
> -	if (!l)
> -		return 0;
> -
> -	if (t->count) {
> -		memcpy(l, t->loc, sizeof(struct location) * t->count);
> -		free_loc_track(t);
> -	}
> -	t->max = max;
> -	t->loc = l;
> -	return 1;
> -}
> -
> -static int add_location(struct loc_track *t, struct kmem_cache *s,
> -				const struct track *track)
> -{
> -	long start, end, pos;
> -	struct location *l;
> -	unsigned long caddr;
> -	unsigned long age = jiffies - track->when;
> -
> -	start = -1;
> -	end = t->count;
> -
> -	for ( ; ; ) {
> -		pos = start + (end - start + 1) / 2;
> -
> -		/*
> -		 * There is nothing at "end". If we end up there
> -		 * we need to add something to before end.
> -		 */
> -		if (pos == end)
> -			break;
> -
> -		caddr = t->loc[pos].addr;
> -		if (track->addr == caddr) {
> -
> -			l = &t->loc[pos];
> -			l->count++;
> -			if (track->when) {
> -				l->sum_time += age;
> -				if (age < l->min_time)
> -					l->min_time = age;
> -				if (age > l->max_time)
> -					l->max_time = age;
> -
> -				if (track->pid < l->min_pid)
> -					l->min_pid = track->pid;
> -				if (track->pid > l->max_pid)
> -					l->max_pid = track->pid;
> -
> -				cpumask_set_cpu(track->cpu,
> -						to_cpumask(l->cpus));
> -			}
> -			node_set(page_to_nid(virt_to_page(track)), l->nodes);
> -			return 1;
> -		}
> -
> -		if (track->addr < caddr)
> -			end = pos;
> -		else
> -			start = pos;
> -	}
> -
> -	/*
> -	 * Not found. Insert new tracking element.
> -	 */
> -	if (t->count >= t->max && !alloc_loc_track(t, 2 * t->max, GFP_ATOMIC))
> -		return 0;
> -
> -	l = t->loc + pos;
> -	if (pos < t->count)
> -		memmove(l + 1, l,
> -			(t->count - pos) * sizeof(struct location));
> -	t->count++;
> -	l->count = 1;
> -	l->addr = track->addr;
> -	l->sum_time = age;
> -	l->min_time = age;
> -	l->max_time = age;
> -	l->min_pid = track->pid;
> -	l->max_pid = track->pid;
> -	cpumask_clear(to_cpumask(l->cpus));
> -	cpumask_set_cpu(track->cpu, to_cpumask(l->cpus));
> -	nodes_clear(l->nodes);
> -	node_set(page_to_nid(virt_to_page(track)), l->nodes);
> -	return 1;
> -}
> -
> -static void process_slab(struct loc_track *t, struct kmem_cache *s,
> -		struct page *page, enum track_item alloc)
> -{
> -	void *addr = page_address(page);
> -	void *p;
> -	unsigned long *map;
> -
> -	map = get_map(s, page);
> -	for_each_object(p, s, addr, page->objects)
> -		if (!test_bit(__obj_to_index(s, addr, p), map))
> -			add_location(t, s, get_track(s, p, alloc));
> -	put_map(map);
> -}
> -
> -static int list_locations(struct kmem_cache *s, char *buf,
> -			  enum track_item alloc)
> -{
> -	int len = 0;
> -	unsigned long i;
> -	struct loc_track t = { 0, 0, NULL };
> -	int node;
> -	struct kmem_cache_node *n;
> -
> -	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
> -			     GFP_KERNEL)) {
> -		return sysfs_emit(buf, "Out of memory\n");
> -	}
> -	/* Push back cpu slabs */
> -	flush_all(s);
> -
> -	for_each_kmem_cache_node(s, node, n) {
> -		unsigned long flags;
> -		struct page *page;
> -
> -		if (!atomic_long_read(&n->nr_slabs))
> -			continue;
> -
> -		spin_lock_irqsave(&n->list_lock, flags);
> -		list_for_each_entry(page, &n->partial, slab_list)
> -			process_slab(&t, s, page, alloc);
> -		list_for_each_entry(page, &n->full, slab_list)
> -			process_slab(&t, s, page, alloc);
> -		spin_unlock_irqrestore(&n->list_lock, flags);
> -	}
> -
> -	for (i = 0; i < t.count; i++) {
> -		struct location *l = &t.loc[i];
> -
> -		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
> -
> -		if (l->addr)
> -			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
> -		else
> -			len += sysfs_emit_at(buf, len, "<not-available>");
> -
> -		if (l->sum_time != l->min_time)
> -			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
> -					     l->min_time,
> -					     (long)div_u64(l->sum_time,
> -							   l->count),
> -					     l->max_time);
> -		else
> -			len += sysfs_emit_at(buf, len, " age=%ld", l->min_time);
> -
> -		if (l->min_pid != l->max_pid)
> -			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
> -					     l->min_pid, l->max_pid);
> -		else
> -			len += sysfs_emit_at(buf, len, " pid=%ld",
> -					     l->min_pid);
> -
> -		if (num_online_cpus() > 1 &&
> -		    !cpumask_empty(to_cpumask(l->cpus)))
> -			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
> -					     cpumask_pr_args(to_cpumask(l->cpus)));
> -
> -		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
> -			len += sysfs_emit_at(buf, len, " nodes=%*pbl",
> -					     nodemask_pr_args(&l->nodes));
> -
> -		len += sysfs_emit_at(buf, len, "\n");
> -	}
> -
> -	free_loc_track(&t);
> -	if (!t.count)
> -		len += sysfs_emit_at(buf, len, "No data\n");
> -
> -	return len;
> -}
>  #endif	/* CONFIG_SLUB_DEBUG */
>  
>  #ifdef SLUB_RESILIENCY_TEST
> @@ -5346,21 +5140,6 @@ static ssize_t validate_store(struct kmem_cache *s,
>  }
>  SLAB_ATTR(validate);
>  
> -static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)
> -{
> -	if (!(s->flags & SLAB_STORE_USER))
> -		return -ENOSYS;
> -	return list_locations(s, buf, TRACK_ALLOC);
> -}
> -SLAB_ATTR_RO(alloc_calls);
> -
> -static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
> -{
> -	if (!(s->flags & SLAB_STORE_USER))
> -		return -ENOSYS;
> -	return list_locations(s, buf, TRACK_FREE);
> -}
> -SLAB_ATTR_RO(free_calls);
>  #endif /* CONFIG_SLUB_DEBUG */
>  
>  #ifdef CONFIG_FAILSLAB
> @@ -5524,8 +5303,6 @@ 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,
> @@ -5814,6 +5591,283 @@ static int __init slab_sysfs_init(void)
>  __initcall(slab_sysfs_init);
>  #endif /* CONFIG_SYSFS */
>  
> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
> +/*
> + * Generate lists of code addresses where slabcache objects are allocated
> + * and freed.
> + */
> +
> +struct location {
> +	unsigned long count;
> +	unsigned long addr;
> +	long long sum_time;
> +	long min_time;
> +	long max_time;
> +	long min_pid;
> +	long max_pid;
> +	DECLARE_BITMAP(cpus, NR_CPUS);
> +	nodemask_t nodes;
> +};
> +
> +struct loc_track {
> +	unsigned long max;
> +	unsigned long count;
> +	struct location *loc;
> +};
> +
> +static struct dentry *slab_debugfs_root;
> +
> +static struct dentry *slab_debugfs_cache;
> +
> +static void free_loc_track(struct loc_track *t)
> +{
> +	if (t->max)
> +		free_pages((unsigned long)t->loc,
> +			get_order(sizeof(struct location) * t->max));
> +}
> +
> +static int alloc_loc_track(struct loc_track *t, unsigned long max, gfp_t flags)
> +{
> +	struct location *l;
> +	int order;
> +
> +	order = get_order(sizeof(struct location) * max);
> +
> +	l = (void *)__get_free_pages(flags, order);
> +	if (!l)
> +		return 0;
> +
> +	if (t->count) {
> +		memcpy(l, t->loc, sizeof(struct location) * t->count);
> +		free_loc_track(t);
> +	}
> +	t->max = max;
> +	t->loc = l;
> +	return 1;
> +}
> +
> +static int add_location(struct loc_track *t, struct kmem_cache *s,
> +				const struct track *track)
> +{
> +	long start, end, pos;
> +	struct location *l;
> +	unsigned long caddr;
> +	unsigned long age = jiffies - track->when;
> +
> +	start = -1;
> +	end = t->count;
> +
> +	for ( ; ; ) {
> +		pos = start + (end - start + 1) / 2;
> +
> +		/*
> +		 * There is nothing at "end". If we end up there
> +		 * we need to add something to before end.
> +		 */
> +		if (pos == end)
> +			break;
> +
> +		caddr = t->loc[pos].addr;
> +		if (track->addr == caddr) {
> +
> +			l = &t->loc[pos];
> +			l->count++;
> +			if (track->when) {
> +				l->sum_time += age;
> +				if (age < l->min_time)
> +					l->min_time = age;
> +				if (age > l->max_time)
> +					l->max_time = age;
> +
> +				if (track->pid < l->min_pid)
> +					l->min_pid = track->pid;
> +				if (track->pid > l->max_pid)
> +					l->max_pid = track->pid;
> +
> +				cpumask_set_cpu(track->cpu,
> +						to_cpumask(l->cpus));
> +			}
> +			node_set(page_to_nid(virt_to_page(track)), l->nodes);
> +			return 1;
> +		}
> +
> +		if (track->addr < caddr)
> +			end = pos;
> +		else
> +			start = pos;
> +	}
> +
> +	/*
> +	 * Not found. Insert new tracking element.
> +	 */
> +	if (t->count >= t->max && !alloc_loc_track(t, 2 * t->max, GFP_ATOMIC))
> +		return 0;
> +
> +	l = t->loc + pos;
> +	if (pos < t->count)
> +		memmove(l + 1, l,
> +			(t->count - pos) * sizeof(struct location));
> +	t->count++;
> +	l->count = 1;
> +	l->addr = track->addr;
> +	l->sum_time = age;
> +	l->min_time = age;
> +	l->max_time = age;
> +	l->min_pid = track->pid;
> +	l->max_pid = track->pid;
> +	cpumask_clear(to_cpumask(l->cpus));
> +	cpumask_set_cpu(track->cpu, to_cpumask(l->cpus));
> +	nodes_clear(l->nodes);
> +	node_set(page_to_nid(virt_to_page(track)), l->nodes);
> +	return 1;
> +}
> +
> +static void process_slab(struct loc_track *t, struct kmem_cache *s,
> +		struct page *page, enum track_item alloc)
> +{
> +	void *addr = page_address(page);
> +	void *p;
> +	unsigned long *map;
> +
> +	map = get_map(s, page);
> +	for_each_object(p, s, addr, page->objects)
> +		if (!test_bit(__obj_to_index(s, addr, p), map))
> +			add_location(t, s, get_track(s, p, alloc));
> +	put_map(map);
> +}
> +
> +static int list_locations(struct seq_file *seq, struct kmem_cache *s,
> +						enum track_item alloc)
> +{
> +	unsigned long i;
> +	struct loc_track t = { 0, 0, NULL };
> +	int node;
> +	struct kmem_cache_node *n;
> +
> +	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
> +			     GFP_KERNEL)) {
> +		seq_puts(seq, "Out of memory\n");
> +		return -ENOMEM;
> +	}
> +	/* Push back cpu slabs */
> +	flush_all(s);
> +
> +	for_each_kmem_cache_node(s, node, n) {
> +		unsigned long flags;
> +		struct page *page;
> +
> +		if (!atomic_long_read(&n->nr_slabs))
> +			continue;
> +
> +		spin_lock_irqsave(&n->list_lock, flags);
> +		list_for_each_entry(page, &n->partial, slab_list)
> +			process_slab(&t, s, page, alloc);
> +		list_for_each_entry(page, &n->full, slab_list)
> +			process_slab(&t, s, page, alloc);
> +		spin_unlock_irqrestore(&n->list_lock, flags);
> +	}
> +
> +	for (i = 0; i < t.count; i++) {
> +		struct location *l = &t.loc[i];
> +
> +		seq_printf(seq, "%7ld ", l->count);
> +
> +		if (l->addr)
> +			seq_printf(seq, "%pS", (void *)l->addr);
> +		else
> +			seq_puts(seq, "<not-available>");
> +
> +		if (l->sum_time != l->min_time) {
> +			seq_printf(seq, " age=%ld/%ld/%ld",
> +				l->min_time,
> +				(long)div_u64(l->sum_time, l->count),
> +				l->max_time);
> +		} else
> +			seq_printf(seq, " age=%ld",
> +				l->min_time);
> +
> +		if (l->min_pid != l->max_pid)
> +			seq_printf(seq, " pid=%ld-%ld",
> +				l->min_pid, l->max_pid);
> +		else
> +			seq_printf(seq, " pid=%ld",
> +				l->min_pid);
> +
> +		if (num_online_cpus() > 1 &&
> +				!cpumask_empty(to_cpumask(l->cpus)))
> +			seq_printf(seq, " cpus=%*pbl",
> +					 cpumask_pr_args(to_cpumask(l->cpus)));
> +
> +		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
> +			seq_printf(seq, " nodes=%*pbl",
> +					 nodemask_pr_args(&l->nodes));
> +
> +		seq_puts(seq, "\n");
> +	}
> +
> +	free_loc_track(&t);
> +	if (!t.count)
> +		seq_puts(seq, "No data\n");
> +	return 0;
> +}
> +
> +static int slab_debug_trace(struct seq_file *seq, void *ignored)
> +{
> +	struct kmem_cache *s = seq->private;
> +
> +	if (!(s->flags & SLAB_STORE_USER))
> +		return 0;
> +
> +	if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_trace") == 0)
> +		return list_locations(seq, s, TRACK_ALLOC);
> +	else
> +		return list_locations(seq, s, TRACK_FREE);
> +
> +	return 0;
> +}
> +
> +static int slab_debug_trace_open(struct inode *inode, struct file *filp)
> +{
> +	return single_open(filp, slab_debug_trace,
> +				file_inode(filp)->i_private);
> +}
> +
> +static const struct file_operations slab_debug_fops = {
> +	.open    = slab_debug_trace_open,
> +	.read    = seq_read,
> +	.llseek  = seq_lseek,
> +	.release = single_release,
> +};
> +
> +static void debugfs_slab_add(struct kmem_cache *s)
> +{
> +	if (unlikely(!slab_debugfs_root))
> +		return;
> +
> +	slab_debugfs_cache = debugfs_create_dir(s->name, slab_debugfs_root);
> +	if (!IS_ERR(slab_debugfs_cache)) {
> +		debugfs_create_file("alloc_trace", 0400,
> +			slab_debugfs_cache, s, &slab_debug_fops);
> +
> +		debugfs_create_file("free_trace", 0400,
> +			slab_debugfs_cache, s, &slab_debug_fops);
> +	}
> +}
> +
> +static void __init slab_debugfs_init(void)
> +{
> +	struct kmem_cache *s;
> +
> +	slab_debugfs_root = debugfs_create_dir("slab", NULL);
> +	if (!IS_ERR(slab_debugfs_root))
> +		list_for_each_entry(s, &slab_caches, list)
> +			debugfs_slab_add(s);
> +	else
> +		pr_err("Cannot create slab debugfs.\n");
> +
> +}
> +__initcall(slab_debugfs_init);
> +#endif
>  /*
>   * The /proc/slabinfo ABI
>   */
>