For high frequency I/O the overhead of threaded interrupts impacts
performance. Add an option to make it configurable, with the default
being hardirq.
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@xxxxxxxxx>
---
drivers/ata/libahci.c | 38 ++++++++++++++++++++++++++++++++++----
1 file changed, 34 insertions(+), 4 deletions(-)
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index c6f098a0435c..69bbd679d6aa 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -57,6 +57,10 @@ MODULE_PARM_DESC(skip_host_reset, "skip global host reset (0=don't skip, 1=skip)
module_param_named(ignore_sss, ahci_ignore_sss, int, 0444);
MODULE_PARM_DESC(ignore_sss, "Ignore staggered spinup flag (0=don't ignore, 1=ignore)");
+static int use_threaded_interrupts;
+module_param(use_threaded_interrupts, int, 0444);
+MODULE_PARM_DESC(, "Defer interrupt handling to a thread (0=don't defer, 1=defer)");
+
static int ahci_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
unsigned hints);
static ssize_t ahci_led_show(struct ata_port *ap, char *buf);
@@ -1826,6 +1830,26 @@ static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
return IRQ_WAKE_THREAD;
}
+static irqreturn_t ahci_multi_irqs_intr_hard(int irq, void *dev_instance)
+{
+ struct ata_port *ap = dev_instance;
+ void __iomem *port_mmio = ahci_port_base(ap);
+ u32 status;
+
+ VPRINTK("ENTER\n");
+
+ status = readl(port_mmio + PORT_IRQ_STAT);
+ writel(status, port_mmio + PORT_IRQ_STAT);
+
+ spin_lock(ap->lock);
+ ahci_handle_port_interrupt(ap, port_mmio, status);
+ spin_unlock(ap->lock);
+
+ VPRINTK("EXIT\n");
+
+ return IRQ_HANDLED;
+}
+
static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
{
unsigned int i, handled = 0;
@@ -2492,10 +2516,16 @@ 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]);
+ if (use_threaded_interrupts)
+ rc = devm_request_threaded_irq(host->dev, irq,
+ ahci_multi_irqs_intr,
+ ahci_port_thread_fn, 0,
+ pp->irq_desc, host->ports[i]);
+ else
+ 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);
--
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