From 58ffacb545f76fc2c65d1fbfa5acf5184a2a09e6 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Sun, 6 Feb 2011 07:28:06 -0500 Subject: [PATCH] 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 --- drivers/block/nvme.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c index 1c3cd6cc0ad9..60c3786bc787 100644 --- a/drivers/block/nvme.c +++ b/drivers/block/nvme.c @@ -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); }