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bh=1kxolnSznagQnuCu9jRXmV8OGgEUIUpt0/kwE2bQdQw=; b=v8l0nBCKYhztJYN/oYLYY3uCkfL4O7/e0Tv+BYHGphqXBqULrR8xjS5kZXSK1iOCPuUHXG //nnHvQ7HobS/rCA== Received: from director2.suse.de ([192.168.254.72]) by imap3-int with ESMTPSA id aFY0NLU2tmCACQAALh3uQQ (envelope-from ); Tue, 01 Jun 2021 13:31:33 +0000 To: Faiyaz Mohammed , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, greg@kroah.com, glittao@gmail.com Cc: vinmenon@codeaurora.org References: <1622542057-14632-1-git-send-email-faiyazm@codeaurora.org> From: Vlastimil Babka Subject: Re: [PATCH v8] mm: slub: move sysfs slab alloc/free interfaces to debugfs Message-ID: <8c6db046-9f12-e670-8fe0-6d34f9328a52@suse.cz> Date: Tue, 1 Jun 2021 15:31:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <1622542057-14632-1-git-send-email-faiyazm@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/1/21 12:07 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. > > Debugfs cache will be created if SLAB_STORE_USER flag is set. > > Rename the alloc_calls/free_calls to alloc_traces/free_traces, > to be inline with what it does. > > Signed-off-by: Faiyaz Mohammed When reading the files I'm getting dmesg errors like this: [ 37.998152] seq_file: buggy .next function slab_debugfs_next did not update position index Don't recall this from previous versions? > diff --git a/mm/slab_common.c b/mm/slab_common.c > index a4a5714..ca39e84 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -449,6 +449,7 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work) > rcu_barrier(); > > list_for_each_entry_safe(s, s2, &to_destroy, list) { > + debugfs_slab_release(s); You should remove this one, you already do the release when queueing the work below. This is not like sysfs where we distinguish _unlink() when queueing and _release when processing the work. > +static struct dentry *slab_debugfs_root; > +struct loc_track t = { 0, 0, NULL }; Ooops, this can't be a global variable, especially when shared without any lock protection - but even with a protection it would be very suboptimal. You'll need to make it a seq_file private, see e.g. here for an example: https://lore.kernel.org/linux-mm/20210521121127.24653-3-glittao@gmail.com/ > static void free_loc_track(struct loc_track *t) > { > if (t->max) > @@ -4825,82 +4840,7 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s, > 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, ""); > - > - 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_DEBUG_FS */ > #endif /* CONFIG_SLUB_DEBUG */ > > #ifdef SLUB_RESILIENCY_TEST > @@ -5350,21 +5290,6 @@ 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 > @@ -5528,8 +5453,6 @@ 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, > @@ -5818,6 +5741,203 @@ static int __init slab_sysfs_init(void) > __initcall(slab_sysfs_init); > #endif /* CONFIG_SYSFS */ > > +#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS) > +static int slab_debugfs_show(struct seq_file *seq, void *v) > +{ > + > + struct location *l; > + unsigned int idx = *(unsigned int *)v; > + > + if (idx < t.count) { > + l = &t.loc[idx]; > + > + seq_printf(seq, "%7ld ", l->count); > + > + if (l->addr) > + seq_printf(seq, "%pS", (void *)l->addr); > + else > + seq_puts(seq, ""); > + > + 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"); > + } > + > + if (t.count == 0) > + seq_puts(seq, "No data\n"); > + > + return 0; > +} > + > +static void slab_debugfs_stop(struct seq_file *seq, void *v) > +{ > + if (!v && t.max) { > + free_loc_track(&t); > + t.max = 0; > + } > +} > + > +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos) > +{ > + loff_t *spos = v; > + > + if (*ppos < t.count) { > + *spos = *spos + 1; > + *ppos = *spos; > + return spos; > + } > + > + return NULL; > +} > + > +static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos) > +{ > + struct kmem_cache_node *n; > + struct kmem_cache *s; > + enum track_item alloc; > + int node; > + loff_t *spos = kmalloc(sizeof(loff_t), GFP_KERNEL); > + > + s = seq->file->f_inode->i_private; > + > + if (!spos) > + return NULL; > + > + if (*ppos == 0) { > + > + t.count = 0; > + t.max = 0; > + t.loc = NULL; > + if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_traces") == 0) > + alloc = TRACK_ALLOC; > + else > + alloc = TRACK_FREE; > + > + if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), > + GFP_KERNEL)) { > + seq_puts(seq, "Out of memory\n"); > + kfree(spos); > + return ERR_PTR(-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); > + } > + } > + > + if (*ppos < t.count) { > + *spos = *ppos; > + return spos; > + } > + > + kfree(spos); > + return NULL; > +} > + > +static const struct seq_operations slab_debugfs_sops = { > + .start = slab_debugfs_start, > + .next = slab_debugfs_next, > + .stop = slab_debugfs_stop, > + .show = slab_debugfs_show > +}; > +DEFINE_SEQ_ATTRIBUTE(slab_debugfs); > + > +static void debugfs_slab_add(struct kmem_cache *s) > +{ > + const char *name; > + struct dentry *slab_cache_dir; > + int unmergeable = slab_unmergeable(s); > + > + if (unlikely(!slab_debugfs_root)) > + return; > + > + if (!unmergeable && disable_higher_order_debug && > + (slub_debug & DEBUG_METADATA_FLAGS)) > + unmergeable = 1; > + > + if (unmergeable) { > + /* > + * Slabcache can never be merged so we can use the name proper. > + * This is typically the case for debug situations. In that > + * case we can catch duplicate names easily. > + */ > + slab_cache_dir = debugfs_lookup(s->name, slab_debugfs_root); > + debugfs_remove_recursive(slab_cache_dir); > + name = s->name; > + } else { > + /* > + * Create a unique name for the slab as a target > + * for the symlinks. > + */ > + name = create_unique_id(s); > + } > + > + slab_cache_dir = debugfs_create_dir(name, slab_debugfs_root); > + > + debugfs_create_file("alloc_traces", 0400, > + slab_cache_dir, s, &slab_debugfs_fops); > + > + debugfs_create_file("free_traces", 0400, > + slab_cache_dir, s, &slab_debugfs_fops); > +} > + > +void debugfs_slab_release(struct kmem_cache *s) > +{ > + debugfs_remove_recursive(debugfs_lookup(s->name, > + slab_debugfs_root)); > +} > + > +static int __init slab_debugfs_init(void) > +{ > + struct kmem_cache *s; > + > + slab_debugfs_root = debugfs_create_dir("slab", NULL); > + > + list_for_each_entry(s, &slab_caches, list) > + if (s->flags & SLAB_STORE_USER) > + debugfs_slab_add(s); > + > + return 0; > + > +} > +__initcall(slab_debugfs_init); > +#endif > /* > * The /proc/slabinfo ABI > */ >