[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>

diff --git a/drivers/scsi/vmw_pvscsi.c b/drivers/scsi/vmw_pvscsi.c
index 7c5abd7..b92ea94 100644 (file)
--- 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) {

diff --git a/drivers/scsi/vmw_pvscsi.h b/drivers/scsi/vmw_pvscsi.h
index a643775..15a9ac6 100644 (file)
--- a/drivers/scsi/vmw_pvscsi.h
+++ b/drivers/scsi/vmw_pvscsi.h
@@ -26,7 +26,7 @@
 
 #include <linux/types.h>
 
-#define PVSCSI_DRIVER_VERSION_STRING   "1.0.3.0-k"
+#define PVSCSI_DRIVER_VERSION_STRING   "1.0.4.0-k"
 
 #define PVSCSI_MAX_NUM_SG_ENTRIES_PER_SEGMENT 128
 
@@ -117,8 +117,9 @@ enum PVSCSICommands {
        PVSCSI_CMD_CONFIG            = 7,
        PVSCSI_CMD_SETUP_MSG_RING    = 8,
        PVSCSI_CMD_DEVICE_UNPLUG     = 9,
+       PVSCSI_CMD_SETUP_REQCALLTHRESHOLD     = 10,
 
-       PVSCSI_CMD_LAST              = 10  /* has to be last */
+       PVSCSI_CMD_LAST              = 11  /* has to be last */
 };
 
 /*
@@ -141,6 +142,14 @@ struct PVSCSICmdDescConfigCmd {
        u32 _pad;
 } __packed;
 
+/*
+ * Command descriptor for PVSCSI_CMD_SETUP_REQCALLTHRESHOLD --
+ */
+
+struct PVSCSICmdDescSetupReqCall {
+       u32 enable;
+} __packed;
+
 enum PVSCSIConfigPageType {
        PVSCSI_CONFIG_PAGE_CONTROLLER = 0x1958,
        PVSCSI_CONFIG_PAGE_PHY        = 0x1959,
@@ -261,7 +270,9 @@ struct PVSCSIRingsState {
        u32     cmpConsIdx;
        u32     cmpNumEntriesLog2;
 
-       u8      _pad[104];
+       u32     reqCallThreshold;
+
+       u8      _pad[100];
 
        u32     msgProdIdx;
        u32     msgConsIdx;