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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>
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1 changed files with 27 additions and 0 deletions
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@ -44,6 +44,9 @@
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static int nvme_major;
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module_param(nvme_major, int, 0);
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static int use_threaded_interrupts;
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module_param(use_threaded_interrupts, int, 0);
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/*
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* Represents an NVM Express device. Each nvme_dev is a PCI function.
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*/
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@ -455,6 +458,25 @@ static irqreturn_t nvme_irq(int irq, void *data)
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return nvme_process_cq(data);
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}
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static irqreturn_t nvme_irq_thread(int irq, void *data)
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{
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irqreturn_t result;
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struct nvme_queue *nvmeq = data;
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spin_lock(&nvmeq->q_lock);
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result = nvme_process_cq(nvmeq);
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spin_unlock(&nvmeq->q_lock);
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return result;
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}
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static irqreturn_t nvme_irq_check(int irq, void *data)
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{
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struct nvme_queue *nvmeq = data;
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struct nvme_completion cqe = nvmeq->cqes[nvmeq->cq_head];
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if ((le16_to_cpu(cqe.status) & 1) != nvmeq->cq_phase)
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return IRQ_NONE;
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return IRQ_WAKE_THREAD;
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}
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static void nvme_abort_command(struct nvme_queue *nvmeq, int cmdid)
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{
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spin_lock_irq(&nvmeq->q_lock);
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@ -630,6 +652,11 @@ static struct nvme_queue *nvme_alloc_queue(struct nvme_dev *dev, int qid,
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static int queue_request_irq(struct nvme_dev *dev, struct nvme_queue *nvmeq,
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const char *name)
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{
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if (use_threaded_interrupts)
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return request_threaded_irq(dev->entry[nvmeq->cq_vector].vector,
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nvme_irq_check, nvme_irq_thread,
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IRQF_DISABLED | IRQF_SHARED,
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name, nvmeq);
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return request_irq(dev->entry[nvmeq->cq_vector].vector, nvme_irq,
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IRQF_DISABLED | IRQF_SHARED, name, nvmeq);
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}
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