L2ARC: Rework write throttling with DWPD rate limiting and parallel writes

include/sys/arc.h

@@ -354,8 +354,6 @@ boolean_t l2arc_range_check_overlap(uint64_t bottom, uint64_t top,
     uint64_t check);
 void l2arc_init(void);
 void l2arc_fini(void);
-void l2arc_start(void);
-void l2arc_stop(void);
 void l2arc_spa_rebuild_start(spa_t *spa);
 void l2arc_spa_rebuild_stop(spa_t *spa);
 

include/sys/arc_impl.h

@@ -41,6 +41,27 @@
 extern "C" {
 #endif
 
+/*
+ * We can feed L2ARC from two states of ARC buffers, mru and mfu,
+ * and each of the state has two types: data and metadata.
+ */
+#define	L2ARC_FEED_TYPES	4
+
+/*
+ * L2ARC state and statistics for persistent marker management.
+ */
+typedef struct l2arc_info {
+	arc_buf_hdr_t	**l2arc_markers[L2ARC_FEED_TYPES];
+	uint64_t	l2arc_total_writes;	/* total writes for reset */
+	uint64_t	l2arc_total_capacity;	/* total L2ARC capacity */
+	uint64_t	l2arc_smallest_capacity; /* smallest device capacity */
+	/*
+	 * Per-device thread coordination for sublist processing
+	 */
+	boolean_t	*l2arc_sublist_busy[L2ARC_FEED_TYPES];
+	kmutex_t	l2arc_sublist_lock;	/* protects busy flags */
+} l2arc_info_t;
+
 /*
  * Note that buffers can be in one of 6 states:
  *	ARC_anon	- anonymous (discussed below)
@@ -421,6 +442,13 @@ typedef struct l2arc_dev {
 	 */
 	zfs_refcount_t		l2ad_lb_count;
 	boolean_t		l2ad_trim_all; /* TRIM whole device */
+	/*
+	 * Per-device feed thread for parallel L2ARC writes
+	 */
+	kthread_t		*l2ad_feed_thread;	/* feed thread handle */
+	boolean_t		l2ad_thread_exit;	/* signal thread exit */
+	kmutex_t		l2ad_feed_thr_lock;	/* thread sleep/wake */
+	kcondvar_t		l2ad_feed_cv;		/* thread wakeup cv */
 } l2arc_dev_t;
 
 /*

include/sys/spa_impl.h

@@ -52,6 +52,7 @@
 #include <sys/dsl_crypt.h>
 #include <sys/zfeature.h>
 #include <sys/zthr.h>
+#include <sys/arc_impl.h>
 #include <sys/dsl_deadlist.h>
 #include <zfeature_common.h>
 
@@ -283,6 +284,7 @@ struct spa {
 	spa_aux_vdev_t	spa_spares;		/* hot spares */
 	spa_aux_vdev_t	spa_l2cache;		/* L2ARC cache devices */
 	boolean_t	spa_aux_sync_uber;	/* need to sync aux uber */
+	l2arc_info_t	spa_l2arc_info;		/* L2ARC state and stats */
 	nvlist_t	*spa_label_features;	/* Features for reading MOS */
 	uint64_t	spa_config_object;	/* MOS object for pool config */
 	uint64_t	spa_config_generation;	/* config generation number */