The patch titled
Subject: mm: shrinkers: introduce debugfs interface for memory shrinkers
has been added to the -mm mm-unstable branch. Its filename is
mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Subject: mm: shrinkers: introduce debugfs interface for memory shrinkers
Date: Tue, 31 May 2022 20:22:23 -0700
This commit introduces the /sys/kernel/debug/shrinker debugfs interface
which provides an ability to observe the state of individual kernel memory
shrinkers.
Because the feature adds some memory overhead (which shouldn't be large
unless there is a huge amount of registered shrinkers), it's guarded by a
config option (enabled by default).
This commit introduces the "count" interface for each shrinker registered
in the system.
The output is in the following format:
<cgroup inode id> <nr of objects on node 0> <nr of objects on node 1>...
<cgroup inode id> <nr of objects on node 0> <nr of objects on node 1>...
...
To reduce the size of output on machines with many thousands cgroups, if
the total number of objects on all nodes is 0, the line is omitted.
If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed as
cgroup inode id. If the shrinker is not numa-aware, 0's are printed for
all nodes except the first one.
This commit gives debugfs entries simple numeric names, which are not very
convenient. The following commit in the series will provide shrinkers
with more meaningful names.
Link: https://lkml.kernel.org/r/20220601032227.4076670-3-roman.gushchin@xxxxxxxxx
Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Reviewed-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Acked-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/shrinker.h | 19 +++-
lib/Kconfig.debug | 9 +
mm/Makefile | 1
mm/shrinker_debug.c | 168 +++++++++++++++++++++++++++++++++++++
mm/vmscan.c | 6 -
5 files changed, 200 insertions(+), 3 deletions(-)
--- a/include/linux/shrinker.h~mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers
+++ a/include/linux/shrinker.h
@@ -73,6 +73,10 @@ struct shrinker {
/* ID in shrinker_idr */
int id;
#endif
+#ifdef CONFIG_SHRINKER_DEBUG
+ int debugfs_id;
+ struct dentry *debugfs_entry;
+#endif
/* objs pending delete, per node */
atomic_long_t *nr_deferred;
};
@@ -94,4 +98,17 @@ extern int register_shrinker(struct shri
extern void unregister_shrinker(struct shrinker *shrinker);
extern void free_prealloced_shrinker(struct shrinker *shrinker);
extern void synchronize_shrinkers(void);
-#endif
+
+#ifdef CONFIG_SHRINKER_DEBUG
+extern int shrinker_debugfs_add(struct shrinker *shrinker);
+extern void shrinker_debugfs_remove(struct shrinker *shrinker);
+#else /* CONFIG_SHRINKER_DEBUG */
+static inline int shrinker_debugfs_add(struct shrinker *shrinker)
+{
+ return 0;
+}
+static inline void shrinker_debugfs_remove(struct shrinker *shrinker)
+{
+}
+#endif /* CONFIG_SHRINKER_DEBUG */
+#endif /* _LINUX_SHRINKER_H */
--- a/lib/Kconfig.debug~mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers
+++ a/lib/Kconfig.debug
@@ -699,6 +699,15 @@ config DEBUG_OBJECTS_ENABLE_DEFAULT
help
Debug objects boot parameter default value
+config SHRINKER_DEBUG
+ default y
+ bool "Enable shrinker debugging support"
+ depends on DEBUG_FS
+ help
+ Say Y to enable the shrinker debugfs interface which provides
+ visibility into the kernel memory shrinkers subsystem.
+ Disable it to avoid an extra memory footprint.
+
config HAVE_DEBUG_KMEMLEAK
bool
--- a/mm/Makefile~mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers
+++ a/mm/Makefile
@@ -133,3 +133,4 @@ obj-$(CONFIG_PAGE_REPORTING) += page_rep
obj-$(CONFIG_IO_MAPPING) += io-mapping.o
obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
+obj-$(CONFIG_SHRINKER_DEBUG) += shrinker_debug.o
--- /dev/null
+++ a/mm/shrinker_debug.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/shrinker.h>
+#include <linux/memcontrol.h>
+
+/* defined in vmscan.c */
+extern struct rw_semaphore shrinker_rwsem;
+extern struct list_head shrinker_list;
+
+static DEFINE_IDA(shrinker_debugfs_ida);
+static struct dentry *shrinker_debugfs_root;
+
+static unsigned long shrinker_count_objects(struct shrinker *shrinker,
+ struct mem_cgroup *memcg,
+ unsigned long *count_per_node)
+{
+ unsigned long nr, total = 0;
+ int nid;
+
+ for_each_node(nid) {
+ if (nid == 0 || (shrinker->flags & SHRINKER_NUMA_AWARE)) {
+ struct shrink_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .nid = nid,
+ .memcg = memcg,
+ };
+
+ nr = shrinker->count_objects(shrinker, &sc);
+ if (nr == SHRINK_EMPTY)
+ nr = 0;
+ } else {
+ nr = 0;
+ }
+
+ count_per_node[nid] = nr;
+ total += nr;
+ }
+
+ return total;
+}
+
+static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
+{
+ struct shrinker *shrinker = m->private;
+ unsigned long *count_per_node;
+ struct mem_cgroup *memcg;
+ unsigned long total;
+ bool memcg_aware;
+ int ret, nid;
+
+ count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
+ if (!count_per_node)
+ return -ENOMEM;
+
+ ret = down_read_killable(&shrinker_rwsem);
+ if (ret) {
+ kfree(count_per_node);
+ return ret;
+ }
+ rcu_read_lock();
+
+ memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ if (memcg && !mem_cgroup_online(memcg))
+ continue;
+
+ total = shrinker_count_objects(shrinker,
+ memcg_aware ? memcg : NULL,
+ count_per_node);
+ if (total) {
+ seq_printf(m, "%lu", mem_cgroup_ino(memcg));
+ for_each_node(nid)
+ seq_printf(m, " %lu", count_per_node[nid]);
+ seq_putc(m, '\n');
+ }
+
+ if (!memcg_aware) {
+ mem_cgroup_iter_break(NULL, memcg);
+ break;
+ }
+
+ if (signal_pending(current)) {
+ mem_cgroup_iter_break(NULL, memcg);
+ ret = -EINTR;
+ break;
+ }
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+
+ rcu_read_unlock();
+ up_read(&shrinker_rwsem);
+
+ kfree(count_per_node);
+ return ret;
+}
+DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
+
+int shrinker_debugfs_add(struct shrinker *shrinker)
+{
+ struct dentry *entry;
+ char buf[16];
+ int id;
+
+ lockdep_assert_held(&shrinker_rwsem);
+
+ /* debugfs isn't initialized yet, add debugfs entries later. */
+ if (!shrinker_debugfs_root)
+ return 0;
+
+ id = ida_alloc(&shrinker_debugfs_ida, GFP_KERNEL);
+ if (id < 0)
+ return id;
+ shrinker->debugfs_id = id;
+
+ snprintf(buf, sizeof(buf), "%d", id);
+
+ /* create debugfs entry */
+ entry = debugfs_create_dir(buf, shrinker_debugfs_root);
+ if (IS_ERR(entry)) {
+ ida_free(&shrinker_debugfs_ida, id);
+ return PTR_ERR(entry);
+ }
+ shrinker->debugfs_entry = entry;
+
+ debugfs_create_file("count", 0220, entry, shrinker,
+ &shrinker_debugfs_count_fops);
+ return 0;
+}
+
+void shrinker_debugfs_remove(struct shrinker *shrinker)
+{
+ lockdep_assert_held(&shrinker_rwsem);
+
+ if (!shrinker->debugfs_entry)
+ return;
+
+ debugfs_remove_recursive(shrinker->debugfs_entry);
+ ida_free(&shrinker_debugfs_ida, shrinker->debugfs_id);
+}
+
+static int __init shrinker_debugfs_init(void)
+{
+ struct shrinker *shrinker;
+ struct dentry *dentry;
+ int ret = 0;
+
+ dentry = debugfs_create_dir("shrinker", NULL);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+ shrinker_debugfs_root = dentry;
+
+ /* Create debugfs entries for shrinkers registered at boot */
+ down_write(&shrinker_rwsem);
+ list_for_each_entry(shrinker, &shrinker_list, list)
+ if (!shrinker->debugfs_entry) {
+ ret = shrinker_debugfs_add(shrinker);
+ if (ret)
+ break;
+ }
+ up_write(&shrinker_rwsem);
+
+ return ret;
+}
+late_initcall(shrinker_debugfs_init);
--- a/mm/vmscan.c~mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers
+++ a/mm/vmscan.c
@@ -190,8 +190,8 @@ static void set_task_reclaim_state(struc
task->reclaim_state = rs;
}
-static LIST_HEAD(shrinker_list);
-static DECLARE_RWSEM(shrinker_rwsem);
+LIST_HEAD(shrinker_list);
+DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_MEMCG
static int shrinker_nr_max;
@@ -650,6 +650,7 @@ void register_shrinker_prepared(struct s
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
shrinker->flags |= SHRINKER_REGISTERED;
+ WARN_ON_ONCE(shrinker_debugfs_add(shrinker));
up_write(&shrinker_rwsem);
}
@@ -677,6 +678,7 @@ void unregister_shrinker(struct shrinker
shrinker->flags &= ~SHRINKER_REGISTERED;
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker);
+ shrinker_debugfs_remove(shrinker);
up_write(&shrinker_rwsem);
kfree(shrinker->nr_deferred);
_
Patches currently in -mm which might be from roman.gushchin@xxxxxxxxx are
mm-memcontrol-introduce-mem_cgroup_ino-and-mem_cgroup_get_from_ino.patch
mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers.patch
mm-shrinkers-provide-shrinkers-with-names.patch
mm-docs-document-shrinker-debugfs.patch
tools-add-memcg_shrinkerpy.patch
mm-shrinkers-add-scan-interface-for-shrinker-debugfs.patch
