@@ -2,6 +2,8 @@
#ifndef _LINUX_SHRINKER_H
#define _LINUX_SHRINKER_H
+struct printbuf;
+
/*
* This struct is used to pass information from page reclaim to the shrinkers.
* We consolidate the values for easier extension later.
@@ -58,10 +60,12 @@ struct shrink_control {
* @flags determine the shrinker abilities, like numa awareness
*/
struct shrinker {
+ char name[32];
unsigned long (*count_objects)(struct shrinker *,
struct shrink_control *sc);
unsigned long (*scan_objects)(struct shrinker *,
struct shrink_control *sc);
+ void (*to_text)(struct printbuf *, struct shrinker *);
long batch; /* reclaim batch size, 0 = default */
int seeks; /* seeks to recreate an obj */
@@ -94,4 +98,5 @@ 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);
+void shrinkers_to_text(struct printbuf *);
#endif
@@ -50,6 +50,7 @@
#include <linux/printk.h>
#include <linux/dax.h>
#include <linux/psi.h>
+#include <linux/printbuf.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -702,6 +703,83 @@ void synchronize_shrinkers(void)
}
EXPORT_SYMBOL(synchronize_shrinkers);
+void shrinker_to_text(struct printbuf *out, struct shrinker *shrinker)
+{
+ struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
+
+ if (shrinker->name[0])
+ pr_buf(out, "%s", shrinker->name);
+ else
+ pr_buf(out, "%ps:", shrinker->scan_objects);
+
+ pr_buf(out, " objects: %lu", shrinker->count_objects(shrinker, &sc));
+ pr_newline(out);
+
+ if (shrinker->to_text) {
+ pr_indent_push(out, 2);
+ shrinker->to_text(out, shrinker);
+ pr_indent_pop(out, 2);
+ pr_newline(out);
+ }
+}
+
+/**
+ * shrinkers_to_text - Report on shrinkers with highest usage
+ *
+ * This reports on the top 10 shrinkers, by object counts, in sorted order:
+ * intended to be used for OOM reporting.
+ */
+void shrinkers_to_text(struct printbuf *out)
+{
+ struct shrinker *shrinker;
+ struct shrinker_by_mem {
+ struct shrinker *shrinker;
+ unsigned long mem;
+ } shrinkers_by_mem[10];
+ int i, nr = 0;
+
+ if (!down_read_trylock(&shrinker_rwsem)) {
+ pr_buf(out, "(couldn't take shrinker lock)");
+ return;
+ }
+
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
+ unsigned long mem = shrinker->count_objects(shrinker, &sc);
+
+ if (!mem || mem == SHRINK_STOP || mem == SHRINK_EMPTY)
+ continue;
+
+ for (i = 0; i < nr; i++)
+ if (mem < shrinkers_by_mem[i].mem)
+ break;
+
+ if (nr < ARRAY_SIZE(shrinkers_by_mem)) {
+ memmove(&shrinkers_by_mem[i + 1],
+ &shrinkers_by_mem[i],
+ sizeof(shrinkers_by_mem[0]) * (nr - i));
+ nr++;
+ } else if (i) {
+ i--;
+ memmove(&shrinkers_by_mem[0],
+ &shrinkers_by_mem[1],
+ sizeof(shrinkers_by_mem[0]) * i);
+ } else {
+ continue;
+ }
+
+ shrinkers_by_mem[i] = (struct shrinker_by_mem) {
+ .shrinker = shrinker,
+ .mem = mem,
+ };
+ }
+
+ for (i = nr - 1; i >= 0; --i)
+ shrinker_to_text(out, shrinkers_by_mem[i].shrinker);
+
+ up_read(&shrinker_rwsem);
+}
+
#define SHRINK_BATCH 128
static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
This adds a new callback method to shrinkers which they can use to describe anything relevant to memory reclaim about their internal state, for example object dirtyness. This uses the new printbufs to output to heap allocated strings, so that the .to_text() methods can be used both for messages logged to the console, and also sysfs/debugfs. This patch also adds shrinkers_to_text(), which reports on the top 10 shrinkers - by object count - in sorted order, to be used in OOM reporting. Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> --- include/linux/shrinker.h | 5 +++ mm/vmscan.c | 78 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 83 insertions(+)