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Commit b80d5ccc authored by Haiyan Hu's avatar Haiyan Hu Committed by Matthew Wilcox
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NVMe: Avoid shift operation when writing cq head doorbell 



Changes the type of dev->db_stride to unsigned and changes the value
stored there to be 1 << the current value. Then there is less
calculation to be done at completion time.

Signed-off-by: default avatarHaiyan Hu <huhaiyan@huawei.com>
Signed-off-by: default avatarMatthew Wilcox <matthew.r.wilcox@intel.com>
parent 2d3c6275

drivers/block/nvme-core.c

+5 −5
Original line number Diff line number Diff line
@@ -775,7 +775,7 @@ static int nvme_process_cq(struct nvme_queue *nvmeq) 
	if (head == nvmeq->cq_head && phase == nvmeq->cq_phase)

		return 0;



	writel(head, nvmeq->q_db + (1 << nvmeq->dev->db_stride));

	writel(head, nvmeq->q_db + nvmeq->dev->db_stride);

	nvmeq->cq_head = head;

	nvmeq->cq_phase = phase;
@@ -1113,7 +1113,7 @@ static struct nvme_queue *nvme_alloc_queue(struct nvme_dev *dev, int qid, 
	init_waitqueue_head(&nvmeq->sq_full);

	init_waitqueue_entry(&nvmeq->sq_cong_wait, nvme_thread);

	bio_list_init(&nvmeq->sq_cong);

	nvmeq->q_db = &dev->dbs[qid << (dev->db_stride + 1)];

	nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];

	nvmeq->q_depth = depth;

	nvmeq->cq_vector = vector;

	nvmeq->q_suspended = 1;
@@ -1149,7 +1149,7 @@ static void nvme_init_queue(struct nvme_queue *nvmeq, u16 qid) 
	nvmeq->sq_tail = 0;

	nvmeq->cq_head = 0;

	nvmeq->cq_phase = 1;

	nvmeq->q_db = &dev->dbs[qid << (dev->db_stride + 1)];

	nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];

	memset(nvmeq->cmdid_data, 0, extra);

	memset((void *)nvmeq->cqes, 0, CQ_SIZE(nvmeq->q_depth));

	nvme_cancel_ios(nvmeq, false);
@@ -1741,7 +1741,7 @@ static int set_queue_count(struct nvme_dev *dev, int count) 


static size_t db_bar_size(struct nvme_dev *dev, unsigned nr_io_queues)

{

	return 4096 + ((nr_io_queues + 1) << (dev->db_stride + 3));

	return 4096 + ((nr_io_queues + 1) * 8 * dev->db_stride);

}



static int nvme_setup_io_queues(struct nvme_dev *dev)
@@ -1958,7 +1958,7 @@ static int nvme_dev_map(struct nvme_dev *dev) 
	if (!dev->bar)

		goto disable;



	dev->db_stride = NVME_CAP_STRIDE(readq(&dev->bar->cap));

	dev->db_stride = 1 << NVME_CAP_STRIDE(readq(&dev->bar->cap));

	dev->dbs = ((void __iomem *)dev->bar) + 4096;



	return 0;

include/linux/nvme.h

+1 −1
Original line number Diff line number Diff line
@@ -80,7 +80,7 @@ struct nvme_dev { 
	struct dma_pool *prp_small_pool;

	int instance;

	int queue_count;

	int db_stride;

	u32 db_stride;

	u32 ctrl_config;

	struct msix_entry *entry;

	struct nvme_bar __iomem *bar;