@@ -40,6 +40,15 @@ MODULE_ALIAS("dmi:*:svnVMware*:*");
MODULE_ALIAS("vmware_vmmemctl");
MODULE_LICENSE("GPL");
+static bool __read_mostly vmwballoon_shrinker_enable;
+module_param(vmwballoon_shrinker_enable, bool, 0444);
+MODULE_PARM_DESC(vmwballoon_shrinker_enable,
+ "Enable non-cooperative out-of-memory protection. Disabled by default as it may degrade performance.");
+
+/* Delay in seconds after shrink before inflation. */
+#define VMBALLOON_SHRINK_DELAY (5)
+
+/* Maximum number of refused pages we accumulate during inflation cycle */
#define VMW_BALLOON_MAX_REFUSED 16
/* Magic number for the balloon mount-point */
@@ -217,12 +226,13 @@ enum vmballoon_stat_general {
VMW_BALLOON_STAT_TIMER,
VMW_BALLOON_STAT_DOORBELL,
VMW_BALLOON_STAT_RESET,
- VMW_BALLOON_STAT_LAST = VMW_BALLOON_STAT_RESET
+ VMW_BALLOON_STAT_SHRINK,
+ VMW_BALLOON_STAT_SHRINK_FREE,
+ VMW_BALLOON_STAT_LAST = VMW_BALLOON_STAT_SHRINK_FREE
};
#define VMW_BALLOON_STAT_NUM (VMW_BALLOON_STAT_LAST + 1)
-
static DEFINE_STATIC_KEY_TRUE(vmw_balloon_batching);
static DEFINE_STATIC_KEY_FALSE(balloon_stat_enabled);
@@ -321,6 +331,15 @@ struct vmballoon {
*/
struct page *page;
+ /**
+ * @shrink_timeout: timeout until the next inflation.
+ *
+ * After an shrink event, indicates the time in jiffies after which
+ * inflation is allowed again. Can be written concurrently with reads,
+ * so must use READ_ONCE/WRITE_ONCE when accessing.
+ */
+ unsigned long shrink_timeout;
+
/* statistics */
struct vmballoon_stats *stats;
@@ -361,6 +380,20 @@ struct vmballoon {
* Lock ordering: @conf_sem -> @comm_lock .
*/
spinlock_t comm_lock;
+
+ /**
+ * @shrinker: shrinker interface that is used to avoid over-inflation.
+ */
+ struct shrinker shrinker;
+
+ /**
+ * @shrinker_registered: whether the shrinker was registered.
+ *
+ * The shrinker interface does not handle gracefully the removal of
+ * shrinker that was not registered before. This indication allows to
+ * simplify the unregistration process.
+ */
+ bool shrinker_registered;
};
static struct vmballoon balloon;
@@ -935,6 +968,10 @@ static int64_t vmballoon_change(struct vmballoon *b)
size - target < vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE))
return 0;
+ /* If an out-of-memory recently occurred, inflation is disallowed. */
+ if (target > size && time_before(jiffies, READ_ONCE(b->shrink_timeout)))
+ return 0;
+
return target - size;
}
@@ -1430,6 +1467,90 @@ static void vmballoon_work(struct work_struct *work)
}
+/**
+ * vmballoon_shrinker_scan() - deflate the balloon due to memory pressure.
+ * @shrinker: pointer to the balloon shrinker.
+ * @sc: page reclaim information.
+ *
+ * Returns: number of pages that were freed during deflation.
+ */
+static unsigned long vmballoon_shrinker_scan(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ struct vmballoon *b = &balloon;
+ unsigned long deflated_frames;
+
+ pr_debug("%s - size: %llu", __func__, atomic64_read(&b->size));
+
+ vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_SHRINK);
+
+ /*
+ * If the lock is also contended for read, we cannot easily reclaim and
+ * we bail out.
+ */
+ if (!down_read_trylock(&b->conf_sem))
+ return 0;
+
+ deflated_frames = vmballoon_deflate(b, sc->nr_to_scan, true);
+
+ vmballoon_stats_gen_add(b, VMW_BALLOON_STAT_SHRINK_FREE,
+ deflated_frames);
+
+ /*
+ * Delay future inflation for some time to mitigate the situations in
+ * which balloon continuously grows and shrinks. Use WRITE_ONCE() since
+ * the access is asynchronous.
+ */
+ WRITE_ONCE(b->shrink_timeout, jiffies + HZ * VMBALLOON_SHRINK_DELAY);
+
+ up_read(&b->conf_sem);
+
+ return deflated_frames;
+}
+
+/**
+ * vmballoon_shrinker_count() - return the number of ballooned pages.
+ * @shrinker: pointer to the balloon shrinker.
+ * @sc: page reclaim information.
+ *
+ * Returns: number of 4k pages that are allocated for the balloon and can
+ * therefore be reclaimed under pressure.
+ */
+static unsigned long vmballoon_shrinker_count(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ struct vmballoon *b = &balloon;
+
+ return atomic64_read(&b->size);
+}
+
+static void vmballoon_unregister_shrinker(struct vmballoon *b)
+{
+ if (b->shrinker_registered)
+ unregister_shrinker(&b->shrinker);
+ b->shrinker_registered = false;
+}
+
+static int vmballoon_register_shrinker(struct vmballoon *b)
+{
+ int r;
+
+ /* Do nothing if the shrinker is not enabled */
+ if (!vmwballoon_shrinker_enable)
+ return 0;
+
+ b->shrinker.scan_objects = vmballoon_shrinker_scan;
+ b->shrinker.count_objects = vmballoon_shrinker_count;
+ b->shrinker.seeks = DEFAULT_SEEKS;
+
+ r = register_shrinker(&b->shrinker);
+
+ if (r == 0)
+ b->shrinker_registered = true;
+
+ return r;
+}
+
/*
* DEBUGFS Interface
*/
@@ -1447,6 +1568,8 @@ static const char * const vmballoon_stat_names[] = {
[VMW_BALLOON_STAT_TIMER] = "timer",
[VMW_BALLOON_STAT_DOORBELL] = "doorbell",
[VMW_BALLOON_STAT_RESET] = "reset",
+ [VMW_BALLOON_STAT_SHRINK] = "shrink",
+ [VMW_BALLOON_STAT_SHRINK_FREE] = "shrinkFree"
};
static int vmballoon_enable_stats(struct vmballoon *b)
@@ -1780,6 +1903,10 @@ static int __init vmballoon_init(void)
INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
+ error = vmballoon_register_shrinker(&balloon);
+ if (error)
+ goto fail;
+
error = vmballoon_debugfs_init(&balloon);
if (error)
goto fail;
@@ -1805,6 +1932,7 @@ static int __init vmballoon_init(void)
return 0;
fail:
+ vmballoon_unregister_shrinker(&balloon);
vmballoon_compaction_deinit(&balloon);
return error;
}
@@ -1819,6 +1947,7 @@ late_initcall(vmballoon_init);
static void __exit vmballoon_exit(void)
{
+ vmballoon_unregister_shrinker(&balloon);
vmballoon_vmci_cleanup(&balloon);
cancel_delayed_work_sync(&balloon.dwork);