[PATCH v4 3/9] scsi: ufshpb: Add region's reads counter

[Avri Altman]

In host control mode, reads are the major source of activation trials.
Keep track of those reads counters, for both active as well inactive
regions.

We reset the read counter upon write - we are only interested in "clean"
reads.  less intuitive however, is that we also reset it upon region's
deactivation.  Region deactivation is often due to the fact that
eviction took place: a region become active on the expense of another.
This is happening when the max-active-regions limit has crossed. If we
don’t reset the counter, we will trigger a lot of trashing of the HPB
database, since few reads (or even one) to the region that was
deactivated, will trigger a re-activation trial.

Keep those counters normalized, as we are using those reads as a
comparative score, to make various decisions.
If during consecutive normalizations an active region has exhaust its
reads - inactivate it.

Signed-off-by: Avri Altman <avri.altman@xxxxxxx>
---
 drivers/scsi/ufs/ufshpb.c | 108 ++++++++++++++++++++++++++++++++------
 drivers/scsi/ufs/ufshpb.h |   7 +++
 2 files changed, 100 insertions(+), 15 deletions(-)

diff --git a/drivers/scsi/ufs/ufshpb.c b/drivers/scsi/ufs/ufshpb.c
index 044fec9854a0..717ccb66b33e 100644
--- a/drivers/scsi/ufs/ufshpb.c
+++ b/drivers/scsi/ufs/ufshpb.c
@@ -16,6 +16,8 @@
 #include "ufshpb.h"
 #include "../sd.h"
 
+#define ACTIVATION_THRESHOLD 4 /* 4 IOs */
+
 /* memory management */
 static struct kmem_cache *ufshpb_mctx_cache;
 static mempool_t *ufshpb_mctx_pool;
@@ -554,6 +556,21 @@ static int ufshpb_issue_pre_req(struct ufshpb_lu *hpb, struct scsi_cmnd *cmd,
 	return ret;
 }
 
+static void ufshpb_update_active_info(struct ufshpb_lu *hpb, int rgn_idx,
+				      int srgn_idx)
+{
+	struct ufshpb_region *rgn;
+	struct ufshpb_subregion *srgn;
+
+	rgn = hpb->rgn_tbl + rgn_idx;
+	srgn = rgn->srgn_tbl + srgn_idx;
+
+	list_del_init(&rgn->list_inact_rgn);
+
+	if (list_empty(&srgn->list_act_srgn))
+		list_add_tail(&srgn->list_act_srgn, &hpb->lh_act_srgn);
+}
+
 /*
  * This function will set up HPB read command using host-side L2P map data.
  */
@@ -600,12 +617,45 @@ int ufshpb_prep(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
 		ufshpb_set_ppn_dirty(hpb, rgn_idx, srgn_idx, srgn_offset,
 				 transfer_len);
 		spin_unlock_irqrestore(&hpb->rgn_state_lock, flags);
+
+		if (hpb->is_hcm) {
+			spin_lock_irqsave(&rgn->rgn_lock, flags);
+			rgn->reads = 0;
+			spin_unlock_irqrestore(&rgn->rgn_lock, flags);
+		}
+
 		return 0;
 	}
 
 	if (!ufshpb_is_support_chunk(hpb, transfer_len))
 		return 0;
 
+	if (hpb->is_hcm) {
+		bool activate = false;
+		/*
+		 * in host control mode, reads are the main source for
+		 * activation trials.
+		 */
+		spin_lock_irqsave(&rgn->rgn_lock, flags);
+		rgn->reads++;
+		if (rgn->reads == ACTIVATION_THRESHOLD)
+			activate = true;
+		spin_unlock_irqrestore(&rgn->rgn_lock, flags);
+		if (activate) {
+			spin_lock_irqsave(&hpb->rsp_list_lock, flags);
+			ufshpb_update_active_info(hpb, rgn_idx, srgn_idx);
+			hpb->stats.rb_active_cnt++;
+			spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
+			dev_dbg(&hpb->sdev_ufs_lu->sdev_dev,
+				"activate region %d-%d\n", rgn_idx, srgn_idx);
+		}
+
+		/* keep those counters normalized */
+		if (rgn->reads > hpb->entries_per_srgn &&
+		    !test_and_set_bit(WORK_PENDING, &hpb->work_data_bits))
+			schedule_work(&hpb->ufshpb_normalization_work);
+	}
+
 	spin_lock_irqsave(&hpb->rgn_state_lock, flags);
 	if (ufshpb_test_ppn_dirty(hpb, rgn_idx, srgn_idx, srgn_offset,
 				   transfer_len)) {
@@ -745,21 +795,6 @@ static int ufshpb_clear_dirty_bitmap(struct ufshpb_lu *hpb,
 	return 0;
 }
 
-static void ufshpb_update_active_info(struct ufshpb_lu *hpb, int rgn_idx,
-				      int srgn_idx)
-{
-	struct ufshpb_region *rgn;
-	struct ufshpb_subregion *srgn;
-
-	rgn = hpb->rgn_tbl + rgn_idx;
-	srgn = rgn->srgn_tbl + srgn_idx;
-
-	list_del_init(&rgn->list_inact_rgn);
-
-	if (list_empty(&srgn->list_act_srgn))
-		list_add_tail(&srgn->list_act_srgn, &hpb->lh_act_srgn);
-}
-
 static void ufshpb_update_inactive_info(struct ufshpb_lu *hpb, int rgn_idx)
 {
 	struct ufshpb_region *rgn;
@@ -1079,6 +1114,14 @@ static void __ufshpb_evict_region(struct ufshpb_lu *hpb,
 
 	ufshpb_cleanup_lru_info(lru_info, rgn);
 
+	if (hpb->is_hcm) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&rgn->rgn_lock, flags);
+		rgn->reads = 0;
+		spin_unlock_irqrestore(&rgn->rgn_lock, flags);
+	}
+
 	for_each_sub_region(rgn, srgn_idx, srgn)
 		ufshpb_purge_active_subregion(hpb, srgn);
 }
@@ -1523,6 +1566,36 @@ static void ufshpb_run_inactive_region_list(struct ufshpb_lu *hpb)
 	spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
 }
 
+static void ufshpb_normalization_work_handler(struct work_struct *work)
+{
+	struct ufshpb_lu *hpb;
+	int rgn_idx;
+
+	hpb = container_of(work, struct ufshpb_lu, ufshpb_normalization_work);
+
+	for (rgn_idx = 0; rgn_idx < hpb->rgns_per_lu; rgn_idx++) {
+		struct ufshpb_region *rgn = hpb->rgn_tbl + rgn_idx;
+
+		if (rgn->reads) {
+			unsigned long flags;
+
+			spin_lock_irqsave(&rgn->rgn_lock, flags);
+			rgn->reads = (rgn->reads >> 1);
+			spin_unlock_irqrestore(&rgn->rgn_lock, flags);
+		}
+
+		if (rgn->rgn_state != HPB_RGN_ACTIVE || rgn->reads)
+			continue;
+
+		/* if region is active but has no reads - inactivate it */
+		spin_lock(&hpb->rsp_list_lock);
+		ufshpb_update_inactive_info(hpb, rgn->rgn_idx);
+		spin_unlock(&hpb->rsp_list_lock);
+	}
+
+	clear_bit(WORK_PENDING, &hpb->work_data_bits);
+}
+
 static void ufshpb_map_work_handler(struct work_struct *work)
 {
 	struct ufshpb_lu *hpb = container_of(work, struct ufshpb_lu, map_work);
@@ -1913,6 +1986,9 @@ static int ufshpb_lu_hpb_init(struct ufs_hba *hba, struct ufshpb_lu *hpb)
 	INIT_LIST_HEAD(&hpb->list_hpb_lu);
 
 	INIT_WORK(&hpb->map_work, ufshpb_map_work_handler);
+	if (hpb->is_hcm)
+		INIT_WORK(&hpb->ufshpb_normalization_work,
+			  ufshpb_normalization_work_handler);
 
 	hpb->map_req_cache = kmem_cache_create("ufshpb_req_cache",
 			  sizeof(struct ufshpb_req), 0, 0, NULL);
@@ -2012,6 +2088,8 @@ static void ufshpb_discard_rsp_lists(struct ufshpb_lu *hpb)
 
 static void ufshpb_cancel_jobs(struct ufshpb_lu *hpb)
 {
+	if (hpb->is_hcm)
+		cancel_work_sync(&hpb->ufshpb_normalization_work);
 	cancel_work_sync(&hpb->map_work);
 }
 
diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
index 8119b1a3d1e5..2fbe928ae7fd 100644
--- a/drivers/scsi/ufs/ufshpb.h
+++ b/drivers/scsi/ufs/ufshpb.h
@@ -121,6 +121,10 @@ struct ufshpb_region {
 	struct list_head list_lru_rgn;
 	unsigned long rgn_flags;
 #define RGN_FLAG_DIRTY 0
+
+	/* region reads - for host mode */
+	spinlock_t rgn_lock;
+	unsigned int reads;
 };
 
 #define for_each_sub_region(rgn, i, srgn)				\
@@ -211,6 +215,9 @@ struct ufshpb_lu {
 
 	/* for selecting victim */
 	struct victim_select_info lru_info;
+	struct work_struct ufshpb_normalization_work;
+	unsigned long work_data_bits;
+#define WORK_PENDING 0
 
 	/* pinned region information */
 	u32 lu_pinned_start;
-- 
2.25.1