scsi: smartpqi: Improve accuracy/performance of raid-bypass-counter

The original implementation of this counter used an atomic variable.
However, this implementation negatively impacted performance in some
configurations.

Switch to using per_cpu variables.

Reviewed-by: Scott Benesh <scott.benesh@microchip.com>
Reviewed-by: Scott Teel <scott.teel@microchip.com>
Reviewed-by: Mike McGowen <mike.mcgowen@microchip.com>
Co-developed-by: Mahesh Rajashekhara <mahesh.rajashekhara@microchip.com>
Signed-off-by: Mahesh Rajashekhara <mahesh.rajashekhara@microchip.com>
Signed-off-by: Kevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: Don Brace <don.brace@microchip.com>
Link: https://lore.kernel.org/r/20240711194704.982400-3-don.brace@microchip.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/smartpqi/smartpqi.h b/drivers/scsi/smartpqi/smartpqi.h
index cdedc271857aae82ef5e25ae2506c4079c6bd6ca..023fbce04e7a6e931c4f7f254eb3c77531fc164a 100644 (file)
--- a/drivers/scsi/smartpqi/smartpqi.h
+++ b/drivers/scsi/smartpqi/smartpqi.h
@@ -1158,7 +1158,7 @@ struct pqi_scsi_dev {
 
        struct pqi_stream_data stream_data[NUM_STREAMS_PER_LUN];
        atomic_t scsi_cmds_outstanding[PQI_MAX_LUNS_PER_DEVICE];
-       unsigned int raid_bypass_cnt;
+       u64 __percpu *raid_bypass_cnt;
 
        struct pqi_tmf_work tmf_work[PQI_MAX_LUNS_PER_DEVICE];
 };

diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c
index 9166dfa1fedc35b39f18697e84134b302907538c..eaebe3cc00aaf7c9b3b4a41ff501c6da2a506eec 100644 (file)
--- a/drivers/scsi/smartpqi/smartpqi_init.c
+++ b/drivers/scsi/smartpqi/smartpqi_init.c
@@ -1508,6 +1508,12 @@ static int pqi_get_raid_map(struct pqi_ctrl_info *ctrl_info,
        if (rc)
                goto error;
 
+       device->raid_bypass_cnt = alloc_percpu(u64);
+       if (!device->raid_bypass_cnt) {
+               rc = -ENOMEM;
+               goto error;
+       }
+
        device->raid_map = raid_map;
 
        return 0;
@@ -2099,6 +2105,10 @@ static void pqi_scsi_update_device(struct pqi_ctrl_info *ctrl_info,
                                /* To prevent this from being freed later. */
                                new_device->raid_map = NULL;
                        }
+                       if (new_device->raid_bypass_enabled && existing_device->raid_bypass_cnt == NULL) {
+                               existing_device->raid_bypass_cnt = new_device->raid_bypass_cnt;
+                               new_device->raid_bypass_cnt = NULL;
+                       }
                        existing_device->raid_bypass_configured = new_device->raid_bypass_configured;
                        existing_device->raid_bypass_enabled = new_device->raid_bypass_enabled;
                }
@@ -2121,6 +2131,7 @@ static void pqi_scsi_update_device(struct pqi_ctrl_info *ctrl_info,
 static inline void pqi_free_device(struct pqi_scsi_dev *device)
 {
        if (device) {
+               free_percpu(device->raid_bypass_cnt);
                kfree(device->raid_map);
                kfree(device);
        }
@@ -6007,6 +6018,7 @@ static int pqi_scsi_queue_command(struct Scsi_Host *shost, struct scsi_cmnd *scm
        u16 hw_queue;
        struct pqi_queue_group *queue_group;
        bool raid_bypassed;
+       u64 *raid_bypass_cnt;
        u8 lun;
 
        scmd->host_scribble = PQI_NO_COMPLETION;
@@ -6053,7 +6065,8 @@ static int pqi_scsi_queue_command(struct Scsi_Host *shost, struct scsi_cmnd *scm
                        rc = pqi_raid_bypass_submit_scsi_cmd(ctrl_info, device, scmd, queue_group);
                        if (rc == 0 || rc == SCSI_MLQUEUE_HOST_BUSY) {
                                raid_bypassed = true;
-                               device->raid_bypass_cnt++;
+                               raid_bypass_cnt = per_cpu_ptr(device->raid_bypass_cnt, smp_processor_id());
+                               (*raid_bypass_cnt)++;
                        }
                }
                if (!raid_bypassed)
@@ -7350,7 +7363,9 @@ static ssize_t pqi_raid_bypass_cnt_show(struct device *dev,
        struct scsi_device *sdev;
        struct pqi_scsi_dev *device;
        unsigned long flags;
-       unsigned int raid_bypass_cnt;
+       u64 raid_bypass_cnt;
+       int cpu;
+       u64 *per_cpu_bypass_cnt_ptr;
 
        sdev = to_scsi_device(dev);
        ctrl_info = shost_to_hba(sdev->host);
@@ -7366,11 +7381,18 @@ static ssize_t pqi_raid_bypass_cnt_show(struct device *dev,
                return -ENODEV;
        }
 
-       raid_bypass_cnt = device->raid_bypass_cnt;
+       raid_bypass_cnt = 0;
+
+       if (device->raid_bypass_cnt) {
+               for_each_online_cpu(cpu) {
+                       per_cpu_bypass_cnt_ptr = per_cpu_ptr(device->raid_bypass_cnt, cpu);
+                       raid_bypass_cnt += *per_cpu_bypass_cnt_ptr;
+               }
+       }
 
        spin_unlock_irqrestore(&ctrl_info->scsi_device_list_lock, flags);
 
-       return scnprintf(buffer, PAGE_SIZE, "0x%x\n", raid_bypass_cnt);
+       return scnprintf(buffer, PAGE_SIZE, "0x%llx\n", raid_bypass_cnt);
 }
 
 static ssize_t pqi_sas_ncq_prio_enable_show(struct device *dev,