[PATCH v19 08/40] dept: add a mechanism to refill the internal memory pools on running out

[Byungchul Park <byungchul@sk.com>]

dept engine works in a constrained environment.  For example, dept
cannot make use of dynamic allocation e.g. kmalloc().  So dept has been
using static pools to keep memory chunks dept uses.

However, dept would barely work once any of the pools gets run out.  So
implemented a mechanism for the refill on the lack, using irq work and
workqueue that fits on the contrained environment.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 kernel/dependency/dept.c          | 108 +++++++++++++++++++++++++-----
 kernel/dependency/dept_internal.h |  19 ++++--
 kernel/dependency/dept_object.h   |  10 +--
 kernel/dependency/dept_proc.c     |   8 +--
 4 files changed, 116 insertions(+), 29 deletions(-)

diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c
index 1c4de1b55730..4b4b28ddc819 100644
--- a/kernel/dependency/dept.c
+++ b/kernel/dependency/dept.c
@@ -75,6 +75,9 @@
 #include <linux/dept.h>
 #include <linux/utsname.h>
 #include <linux/kernel.h>
+#include <linux/workqueue.h>
+#include <linux/irq_work.h>
+#include <linux/vmalloc.h>
 #include "dept_internal.h"
 
 static int dept_stop;
@@ -143,9 +146,11 @@ static inline struct dept_task *dept_task(void)
 		}							\
 	})
 
-#define DEPT_INFO_ONCE(s...) pr_warn_once("DEPT_INFO_ONCE: " s)
+#define DEPT_INFO_ONCE(s...)	pr_warn_once("DEPT_INFO_ONCE: " s)
+#define DEPT_INFO(s...)		pr_warn("DEPT_INFO: " s)
 
 static arch_spinlock_t dept_spin = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+static arch_spinlock_t dept_pool_spin = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 
 /*
  * The DEPT internal engine should be cautious when using external functions
@@ -268,6 +273,7 @@ static bool valid_key(struct dept_key *k)
 
 #define OBJECT(id, nr)							\
 static struct dept_##id spool_##id[nr];					\
+static struct dept_##id rpool_##id[nr];					\
 static DEFINE_PER_CPU(struct llist_head, lpool_##id);
 	#include "dept_object.h"
 #undef OBJECT
@@ -276,14 +282,74 @@ struct dept_pool dept_pool[OBJECT_NR] = {
 #define OBJECT(id, nr) {						\
 	.name = #id,							\
 	.obj_sz = sizeof(struct dept_##id),				\
-	.obj_nr = ATOMIC_INIT(nr),					\
+	.obj_nr = nr,							\
+	.tot_nr = nr,							\
+	.acc_sz = ATOMIC_INIT(sizeof(spool_##id) + sizeof(rpool_##id)), \
 	.node_off = offsetof(struct dept_##id, pool_node),		\
 	.spool = spool_##id,						\
+	.rpool = rpool_##id,						\
 	.lpool = &lpool_##id, },
 	#include "dept_object.h"
 #undef OBJECT
 };
 
+static void dept_wq_work_fn(struct work_struct *work)
+{
+	int i;
+
+	for (i = 0; i < OBJECT_NR; i++) {
+		struct dept_pool *p = dept_pool + i;
+		int sz = p->tot_nr * p->obj_sz;
+		void *rpool;
+		bool need;
+
+		local_irq_disable();
+		arch_spin_lock(&dept_pool_spin);
+		need = !p->rpool;
+		arch_spin_unlock(&dept_pool_spin);
+		local_irq_enable();
+
+		if (!need)
+			continue;
+
+		rpool = vmalloc(sz);
+
+		if (!rpool) {
+			DEPT_STOP("Failed to extend internal resources.\n");
+			break;
+		}
+
+		local_irq_disable();
+		arch_spin_lock(&dept_pool_spin);
+		if (!p->rpool) {
+			p->rpool = rpool;
+			rpool = NULL;
+			atomic_add(sz, &p->acc_sz);
+		}
+		arch_spin_unlock(&dept_pool_spin);
+		local_irq_enable();
+
+		if (rpool)
+			vfree(rpool);
+		else
+			DEPT_INFO("Dept object(%s) just got refilled successfully.\n", p->name);
+	}
+}
+
+static DECLARE_WORK(dept_wq_work, dept_wq_work_fn);
+
+static void dept_irq_work_fn(struct irq_work *w)
+{
+	schedule_work(&dept_wq_work);
+}
+
+static DEFINE_IRQ_WORK(dept_irq_work, dept_irq_work_fn);
+
+static void request_rpool_refill(void)
+{
+	irq_work_queue(&dept_irq_work);
+}
+
 /*
  * We can use llist regardless of whether CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
  * is enabled, because NMI and other contexts on the same CPU never run
@@ -319,19 +385,31 @@ static void *from_pool(enum object_t t)
 	/*
 	 * Try static pool.
 	 */
-	if (atomic_read(&p->obj_nr) > 0) {
-		int idx = atomic_dec_return(&p->obj_nr);
+	arch_spin_lock(&dept_pool_spin);
+
+	if (!p->obj_nr) {
+		p->spool = p->rpool;
+		p->obj_nr = p->rpool ? p->tot_nr : 0;
+		p->rpool = NULL;
+		request_rpool_refill();
+	}
+
+	if (p->obj_nr) {
+		void *ret;
+
+		p->obj_nr--;
+		ret = p->spool + (p->obj_nr * p->obj_sz);
+		arch_spin_unlock(&dept_pool_spin);
 
-		if (idx >= 0)
-			return p->spool + (idx * p->obj_sz);
+		return ret;
 	}
+	arch_spin_unlock(&dept_pool_spin);
 
-	DEPT_INFO_ONCE("---------------------------------------------\n"
-		"  Some of Dept internal resources are run out.\n"
-		"  Dept might still work if the resources get freed.\n"
-		"  However, the chances are Dept will suffer from\n"
-		"  the lack from now. Needs to extend the internal\n"
-		"  resource pools. Ask max.byungchul.park@gmail.com\n");
+	DEPT_INFO("------------------------------------------\n"
+		"  Dept object(%s) is run out.\n"
+		"  Dept is trying to refill the object.\n"
+		"  Nevertheless, if it fails, Dept will stop.\n",
+		p->name);
 	return NULL;
 }
 
@@ -2957,8 +3035,8 @@ void __init dept_init(void)
 	pr_info("... DEPT_MAX_ECXT_HELD  : %d\n", DEPT_MAX_ECXT_HELD);
 	pr_info("... DEPT_MAX_SUBCLASSES : %d\n", DEPT_MAX_SUBCLASSES);
 #define OBJECT(id, nr)							\
-	pr_info("... memory used by %s: %zu KB\n",			\
-	       #id, B2KB(sizeof(struct dept_##id) * nr));
+	pr_info("... memory initially used by %s: %zu KB\n",		\
+	       #id, B2KB(sizeof(spool_##id) + sizeof(rpool_##id)));
 	#include "dept_object.h"
 #undef OBJECT
 #define HASH(id, bits)							\
@@ -2966,6 +3044,6 @@ void __init dept_init(void)
 	       #id, B2KB(sizeof(struct hlist_head) * (1 << (bits))));
 	#include "dept_hash.h"
 #undef HASH
-	pr_info("... total memory used by objects and hashs: %zu KB\n", B2KB(mem_total));
+	pr_info("... total memory initially used by objects and hashs: %zu KB\n", B2KB(mem_total));
 	pr_info("... per task memory footprint: %zu bytes\n", sizeof(struct dept_task));
 }
diff --git a/kernel/dependency/dept_internal.h b/kernel/dependency/dept_internal.h
index f5023365b3fd..051d4ee4e6e1 100644
--- a/kernel/dependency/dept_internal.h
+++ b/kernel/dependency/dept_internal.h
@@ -26,9 +26,19 @@ struct dept_pool {
 	size_t				obj_sz;
 
 	/*
-	 * the number of the static array
+	 * the remaining number of the object in spool
 	 */
-	atomic_t			obj_nr;
+	int				obj_nr;
+
+	/*
+	 * the number of the object in spool
+	 */
+	int				tot_nr;
+
+	/*
+	 * accumulated amount of memory used by the object in byte
+	 */
+	atomic_t			acc_sz;
 
 	/*
 	 * offset of ->pool_node
@@ -38,9 +48,10 @@ struct dept_pool {
 	/*
 	 * pointer to the pool
 	 */
-	void				*spool;
+	void				*spool; /* static pool */
+	void				*rpool; /* reserved pool */
 	struct llist_head		boot_pool;
-	struct llist_head __percpu	*lpool;
+	struct llist_head __percpu	*lpool; /* local pool */
 };
 
 struct dept_ecxt;
diff --git a/kernel/dependency/dept_object.h b/kernel/dependency/dept_object.h
index 0b7eb16fe9fb..4f936adfa8ee 100644
--- a/kernel/dependency/dept_object.h
+++ b/kernel/dependency/dept_object.h
@@ -6,8 +6,8 @@
  * nr: # of the object that should be kept in the pool.
  */
 
-OBJECT(dep, 1024 * 8)
-OBJECT(class, 1024 * 8)
-OBJECT(stack, 1024 * 32)
-OBJECT(ecxt, 1024 * 16)
-OBJECT(wait, 1024 * 32)
+OBJECT(dep, 1024 * 4 * 2)
+OBJECT(class, 1024 * 4)
+OBJECT(stack, 1024 * 4 * 8)
+OBJECT(ecxt, 1024 * 4 * 2)
+OBJECT(wait, 1024 * 4 * 4)
diff --git a/kernel/dependency/dept_proc.c b/kernel/dependency/dept_proc.c
index 97beaf397715..f28992834588 100644
--- a/kernel/dependency/dept_proc.c
+++ b/kernel/dependency/dept_proc.c
@@ -74,12 +74,10 @@ static int dept_stats_show(struct seq_file *m, void *v)
 {
 	int r;
 
-	seq_puts(m, "Availability in the static pools:\n\n");
+	seq_puts(m, "Accumulated amount of memory used by pools:\n\n");
 #define OBJECT(id, nr)							\
-	r = atomic_read(&dept_pool[OBJECT_##id].obj_nr);		\
-	if (r < 0)							\
-		r = 0;							\
-	seq_printf(m, "%s\t%d/%d(%d%%)\n", #id, r, nr, (r * 100) / (nr));
+	r = atomic_read(&dept_pool[OBJECT_##id].acc_sz);		\
+	seq_printf(m, "%s\t%d KB\n", #id, r / 1024);
 	#include "dept_object.h"
 #undef  OBJECT
 
-- 
2.17.1