Le 09/05/2022 à 20:38, Roman Gushchin a écrit :
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.
Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
---
include/linux/shrinker.h | 19 ++++-
lib/Kconfig.debug | 9 +++
mm/Makefile | 1 +
mm/shrinker_debug.c | 171 +++++++++++++++++++++++++++++++++++++++
mm/vmscan.c | 6 +-
5 files changed, 203 insertions(+), 3 deletions(-)
create mode 100644 mm/shrinker_debug.c
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 76fbf92b04d9..2ced8149c513 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -72,6 +72,10 @@ struct shrinker {
#ifdef CONFIG_MEMCG
/* 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 shrinker *shrinker);
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 */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3fd7a2e9eaf1..5fa65a649798 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -733,6 +733,15 @@ config SLUB_STATS
out which slabs are relevant to a particular load.
Try running: slabinfo -DA
+config SHRINKER_DEBUG
+ default y
The previous version of the serie had default 'n'.
Is it intentional to have it now activated by default? It looked more
like a tuning functionality when fine grained mangement of shrinker is
needed.
+ 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.
+
[...]
