[SCSI] vmw_pvscsi: Add support for I/O requests coalescing.

This change allows pvscsi driver to coalesce I/O requests
before issuing them. The number of I/O's coalesced can be
dynamically configured based on the workload.

Signed-off-by: Rishi Mehta <rmehta@vmware.com>
Signed-off-by: Arvind Kumar <arvindkumar@vmware.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 46 insertions, 3 deletions

diff --git a/drivers/scsi/vmw_pvscsi.c b/drivers/scsi/vmw_pvscsi.c
index 7c5abd7f6c67..b92ea94be98f 100644
--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -72,6 +72,7 @@ struct pvscsi_adapter {
         bool                            use_msi;
         bool                            use_msix;
         bool                            use_msg;
+        bool                            use_req_threshold;
 
         spinlock_t                      hw_lock;
 
@@ -109,6 +110,7 @@ static int pvscsi_cmd_per_lun    = PVSCSI_DEFAULT_QUEUE_DEPTH;
 static bool pvscsi_disable_msi;
 static bool pvscsi_disable_msix;
 static bool pvscsi_use_msg       = true;
+static bool pvscsi_use_req_threshold = true;
 
 #define PVSCSI_RW (S_IRUSR | S_IWUSR)
 
@@ -133,6 +135,10 @@ MODULE_PARM_DESC(disable_msix, "Disable MSI-X use in driver - (default=0)");
 module_param_named(use_msg, pvscsi_use_msg, bool, PVSCSI_RW);
 MODULE_PARM_DESC(use_msg, "Use msg ring when available - (default=1)");
 
+module_param_named(use_req_threshold, pvscsi_use_req_threshold,
+                   bool, PVSCSI_RW);
+MODULE_PARM_DESC(use_req_threshold, "Use driver-based request coalescing if configured - (default=1)");
+
 static const struct pci_device_id pvscsi_pci_tbl[] = {
         { PCI_VDEVICE(VMWARE, PCI_DEVICE_ID_VMWARE_PVSCSI) },
         { 0 }
@@ -282,10 +288,15 @@ static int scsi_is_rw(unsigned char op)
 static void pvscsi_kick_io(const struct pvscsi_adapter *adapter,
                            unsigned char op)
 {
-        if (scsi_is_rw(op))
-                pvscsi_kick_rw_io(adapter);
-        else
+        if (scsi_is_rw(op)) {
+                struct PVSCSIRingsState *s = adapter->rings_state;
+
+                if (!adapter->use_req_threshold ||
+                    s->reqProdIdx - s->reqConsIdx >= s->reqCallThreshold)
+                        pvscsi_kick_rw_io(adapter);
+        } else {
                 pvscsi_process_request_ring(adapter);
+        }
 }
 
 static void ll_adapter_reset(const struct pvscsi_adapter *adapter)
@@ -1077,6 +1088,34 @@ static int pvscsi_setup_msg_workqueue(struct pvscsi_adapter *adapter)
         return 1;
 }
 
+static bool pvscsi_setup_req_threshold(struct pvscsi_adapter *adapter,
+                                      bool enable)
+{
+        u32 val;
+
+        if (!pvscsi_use_req_threshold)
+                return false;
+
+        pvscsi_reg_write(adapter, PVSCSI_REG_OFFSET_COMMAND,
+                         PVSCSI_CMD_SETUP_REQCALLTHRESHOLD);
+        val = pvscsi_reg_read(adapter, PVSCSI_REG_OFFSET_COMMAND_STATUS);
+        if (val == -1) {
+                printk(KERN_INFO "vmw_pvscsi: device does not support req_threshold\n");
+                return false;
+        } else {
+                struct PVSCSICmdDescSetupReqCall cmd_msg = { 0 };
+                cmd_msg.enable = enable;
+                printk(KERN_INFO
+                       "vmw_pvscsi: %sabling reqCallThreshold\n",
+                        enable ? "en" : "dis");
+                pvscsi_write_cmd_desc(adapter,
+                                      PVSCSI_CMD_SETUP_REQCALLTHRESHOLD,
+                                      &cmd_msg, sizeof(cmd_msg));
+                return pvscsi_reg_read(adapter,
+                                       PVSCSI_REG_OFFSET_COMMAND_STATUS) != 0;
+        }
+}
+
 static irqreturn_t pvscsi_isr(int irq, void *devp)
 {
         struct pvscsi_adapter *adapter = devp;
@@ -1416,6 +1455,10 @@ static int pvscsi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
                 flags = IRQF_SHARED;
         }
 
+        adapter->use_req_threshold = pvscsi_setup_req_threshold(adapter, true);
+        printk(KERN_DEBUG "vmw_pvscsi: driver-based request coalescing %sabled\n",
+               adapter->use_req_threshold ? "en" : "dis");
+
         error = request_irq(adapter->irq, pvscsi_isr, flags,
                             "vmw_pvscsi", adapter);
         if (error) {