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Subject[PATCH 4/8] scsi: ufshpb: Make eviction depends on region's reads
Date
In host mode, eviction is considered an extreme measure.
verify that the entering region has enough reads, and the exiting
region has much less reads.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
drivers/scsi/ufs/ufshpb.c | 44 ++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/ufs/ufshpb.c b/drivers/scsi/ufs/ufshpb.c
index 51c3607166bc..a16c0f2d5fac 100644
--- a/drivers/scsi/ufs/ufshpb.c
+++ b/drivers/scsi/ufs/ufshpb.c
@@ -18,6 +18,7 @@

#define WORK_PENDING 0
#define ACTIVATION_THRSHLD 4 /* 4 IOs */
+#define EVICTION_THRSHLD (ACTIVATION_THRSHLD << 6) /* 256 IOs */

/* memory management */
static struct kmem_cache *ufshpb_mctx_cache;
@@ -639,6 +640,14 @@ static struct ufshpb_region *ufshpb_victim_lru_info(struct ufshpb_lu *hpb)
if (ufshpb_check_srgns_issue_state(hpb, rgn))
continue;

+ /*
+ * in host control mode, verify that the exiting region
+ * has less reads
+ */
+ if (ufshpb_mode == HPB_HOST_CONTROL &&
+ atomic64_read(&rgn->reads) > (EVICTION_THRSHLD >> 1))
+ continue;
+
victim_rgn = rgn;
break;
}
@@ -789,7 +798,7 @@ static int ufshpb_issue_map_req(struct ufshpb_lu *hpb,

static int ufshpb_add_region(struct ufshpb_lu *hpb, struct ufshpb_region *rgn)
{
- struct ufshpb_region *victim_rgn;
+ struct ufshpb_region *victim_rgn = NULL;
struct victim_select_info *lru_info = &hpb->lru_info;
unsigned long flags;
int ret = 0;
@@ -817,6 +826,17 @@ static int ufshpb_add_region(struct ufshpb_lu *hpb, struct ufshpb_region *rgn)
* because the device could detect this region
* by not issuing HPB_READ
*/
+
+ /*
+ * in host control mode, verify that the entering
+ * region has enough reads
+ */
+ if (ufshpb_mode == HPB_HOST_CONTROL &&
+ atomic64_read(&rgn->reads) < EVICTION_THRSHLD) {
+ ret = -EACCES;
+ goto out;
+ }
+
victim_rgn = ufshpb_victim_lru_info(hpb);
if (!victim_rgn) {
dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
@@ -1024,8 +1044,13 @@ static void ufshpb_run_active_subregion_list(struct ufshpb_lu *hpb)

rgn = hpb->rgn_tbl + srgn->rgn_idx;
ret = ufshpb_add_region(hpb, rgn);
- if (ret)
- goto active_failed;
+ if (ret) {
+ if (ret == -EACCES) {
+ spin_lock_irqsave(&hpb->rsp_list_lock, flags);
+ continue;
+ }
+ goto add_region_failed;
+ }

ret = ufshpb_issue_map_req(hpb, rgn, srgn);
if (ret) {
@@ -1039,9 +1064,22 @@ static void ufshpb_run_active_subregion_list(struct ufshpb_lu *hpb)
spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
return;

+add_region_failed:
+ if (ufshpb_mode == HPB_HOST_CONTROL) {
+ /*
+ * In host control mode, it is common that eviction trials
+ * fail, either because the entering region didn't have enough
+ * reads, or a poor-performing exiting region wasn't found.
+ * No need to re-insert those regions to the "to-be-activated"
+ * list.
+ */
+ return;
+ }
+
active_failed:
dev_err(&hpb->sdev_ufs_lu->sdev_dev, "failed to activate region %d - %d, will retry\n",
rgn->rgn_idx, srgn->srgn_idx);
+
spin_lock_irqsave(&hpb->rsp_list_lock, flags);
ufshpb_add_active_list(hpb, rgn, srgn);
spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
--
2.25.1
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