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NVMe: Add a module parameter to use a threaded interrupt 

We're currently calling bio_endio from hard interrupt context.  This is
not a good idea for preemptible kernels as it will cause longer latencies.
Using a threaded interrupt will run the entire queue processing mechanism
(including bio_endio) in a thread, which can be preempted.  Unfortuantely,
it also adds about 7us of latency to the single-I/O case, so make it a
module parameter for the moment.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
This commit is contained in:
Matthew Wilcox 2011-02-06 07:28:06 -05:00
parent b1ad37efca
commit 58ffacb545
1 changed files with 27 additions and 0 deletions
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27
drivers/block/nvme.c
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@ -44,6 +44,9 @@
static int nvme_major;
module_param(nvme_major, int, 0);
static int use_threaded_interrupts;
module_param(use_threaded_interrupts, int, 0);
/*
* Represents an NVM Express device. Each nvme_dev is a PCI function.
*/
@ -455,6 +458,25 @@ static irqreturn_t nvme_irq(int irq, void *data)
return nvme_process_cq(data);
}
static irqreturn_t nvme_irq_thread(int irq, void *data)
{
irqreturn_t result;
struct nvme_queue *nvmeq = data;
spin_lock(&nvmeq->q_lock);
result = nvme_process_cq(nvmeq);
spin_unlock(&nvmeq->q_lock);
return result;
}
static irqreturn_t nvme_irq_check(int irq, void *data)
{
struct nvme_queue *nvmeq = data;
struct nvme_completion cqe = nvmeq->cqes[nvmeq->cq_head];
if ((le16_to_cpu(cqe.status) & 1) != nvmeq->cq_phase)
return IRQ_NONE;
return IRQ_WAKE_THREAD;
}
static void nvme_abort_command(struct nvme_queue *nvmeq, int cmdid)
{
spin_lock_irq(&nvmeq->q_lock);
@ -630,6 +652,11 @@ static struct nvme_queue *nvme_alloc_queue(struct nvme_dev *dev, int qid,
static int queue_request_irq(struct nvme_dev *dev, struct nvme_queue *nvmeq,
const char *name)
{
if (use_threaded_interrupts)
return request_threaded_irq(dev->entry[nvmeq->cq_vector].vector,
nvme_irq_check, nvme_irq_thread,
IRQF_DISABLED | IRQF_SHARED,
name, nvmeq);
return request_irq(dev->entry[nvmeq->cq_vector].vector, nvme_irq,
IRQF_DISABLED | IRQF_SHARED, name, nvmeq);
}