ahci: switch from 'threaded' to 'hardirq' interrupt handling

For high frequency I/O the overhead of threaded interrupts impacts
performance.  A quick out-of-the-box test (i.e. no affinity tuning)
shows ~10% random read performance at ~20% less cpu.  The cpu wins
appear to be from reduced lock contention.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 0a5645f..1b6c7cc 100644 (file)
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1796,41 +1796,24 @@ static void ahci_port_intr(struct ata_port *ap)
        ahci_handle_port_interrupt(ap, port_mmio, status);
 }
 
-static irqreturn_t ahci_port_thread_fn(int irq, void *dev_instance)
+static irqreturn_t ahci_multi_irqs_intr_hard(int irq, void *dev_instance)
 {
        struct ata_port *ap = dev_instance;
-       struct ahci_port_priv *pp = ap->private_data;
        void __iomem *port_mmio = ahci_port_base(ap);
        u32 status;
 
-       status = atomic_xchg(&pp->intr_status, 0);
-       if (!status)
-               return IRQ_NONE;
-
-       spin_lock_bh(ap->lock);
-       ahci_handle_port_interrupt(ap, port_mmio, status);
-       spin_unlock_bh(ap->lock);
-
-       return IRQ_HANDLED;
-}
-
-static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
-{
-       struct ata_port *ap = dev_instance;
-       void __iomem *port_mmio = ahci_port_base(ap);
-       struct ahci_port_priv *pp = ap->private_data;
-       u32 status;
-
        VPRINTK("ENTER\n");
 
        status = readl(port_mmio + PORT_IRQ_STAT);
        writel(status, port_mmio + PORT_IRQ_STAT);
 
-       atomic_or(status, &pp->intr_status);
+       spin_lock(ap->lock);
+       ahci_handle_port_interrupt(ap, port_mmio, status);
+       spin_unlock(ap->lock);
 
        VPRINTK("EXIT\n");
 
-       return IRQ_WAKE_THREAD;
+       return IRQ_HANDLED;
 }
 
 static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
@@ -2499,10 +2482,9 @@ static int ahci_host_activate_multi_irqs(struct ata_host *host,
                        continue;
                }
 
-               rc = devm_request_threaded_irq(host->dev, irq,
-                                              ahci_multi_irqs_intr,
-                                              ahci_port_thread_fn, 0,
-                                              pp->irq_desc, host->ports[i]);
+               rc = devm_request_irq(host->dev, irq, ahci_multi_irqs_intr_hard,
+                               0, pp->irq_desc, host->ports[i]);
+
                if (rc)
                        return rc;
                ata_port_desc(host->ports[i], "irq %d", irq);