Commit d977506f authored by Caleb Sander Mateos's avatar Caleb Sander Mateos Committed by Christoph Hellwig
Browse files

nvme-pci: make PRP list DMA pools per-NUMA-node 

NVMe commands with over 8 KB of discontiguous data allocate PRP list
pages from the per-nvme_device dma_pool prp_page_pool or prp_small_pool.
Each call to dma_pool_alloc() and dma_pool_free() takes the per-dma_pool
spinlock. These device-global spinlocks are a significant source of
contention when many CPUs are submitting to the same NVMe devices. On a
workload issuing 32 KB reads from 16 CPUs (8 hypertwin pairs) across 2
NUMA nodes to 23 NVMe devices, we observed 2.4% of CPU time spent in
_raw_spin_lock_irqsave called from dma_pool_alloc and dma_pool_free.

Ideally, the dma_pools would be per-hctx to minimize contention. But
that could impose considerable resource costs in a system with many NVMe
devices and CPUs.

As a compromise, allocate per-NUMA-node PRP list DMA pools. Map each
nvme_queue to the set of DMA pools corresponding to its device and its
hctx's NUMA node. This reduces the _raw_spin_lock_irqsave overhead by
about half, to 1.2%. Preventing the sharing of PRP list pages across
NUMA nodes also makes them cheaper to initialize.

Link: https://lore.kernel.org/linux-nvme/CADUfDZqa=OOTtTTznXRDmBQo1WrFcDw1hBA7XwM7hzJ-hpckcA@mail.gmail.com/T/#u


Signed-off-by: default avatarCaleb Sander Mateos <csander@purestorage.com>
Reviewed-by: default avatarJens Axboe <axboe@kernel.dk>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Reviewed-by: default avatarKanchan Joshi <joshi.k@samsung.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent b9d1ec53

drivers/nvme/host/pci.c

+84 −60
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/mm.h>

#include <linux/module.h>

#include <linux/mutex.h>

#include <linux/nodemask.h>

#include <linux/once.h>

#include <linux/pci.h>

#include <linux/suspend.h>
@@ -112,6 +113,11 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown); 
static void nvme_delete_io_queues(struct nvme_dev *dev);

static void nvme_update_attrs(struct nvme_dev *dev);



struct nvme_prp_dma_pools {

	struct dma_pool *large;

	struct dma_pool *small;

};



/*

 * Represents an NVM Express device.  Each nvme_dev is a PCI function.

 */
@@ -121,8 +127,6 @@ struct nvme_dev { 
	struct blk_mq_tag_set admin_tagset;

	u32 __iomem *dbs;

	struct device *dev;

	struct dma_pool *prp_page_pool;

	struct dma_pool *prp_small_pool;

	unsigned online_queues;

	unsigned max_qid;

	unsigned io_queues[HCTX_MAX_TYPES];
@@ -162,6 +166,7 @@ struct nvme_dev { 
	unsigned int nr_allocated_queues;

	unsigned int nr_write_queues;

	unsigned int nr_poll_queues;

	struct nvme_prp_dma_pools prp_pools[];

};



static int io_queue_depth_set(const char *val, const struct kernel_param *kp)
@@ -191,6 +196,7 @@ static inline struct nvme_dev *to_nvme_dev(struct nvme_ctrl *ctrl) 
 */

struct nvme_queue {

	struct nvme_dev *dev;

	struct nvme_prp_dma_pools prp_pools;

	spinlock_t sq_lock;

	void *sq_cmds;

	 /* only used for poll queues: */
@@ -397,15 +403,64 @@ static int nvme_pci_npages_prp(void) 
	return DIV_ROUND_UP(8 * nprps, NVME_CTRL_PAGE_SIZE - 8);

}



static struct nvme_prp_dma_pools *

nvme_setup_prp_pools(struct nvme_dev *dev, unsigned numa_node)

{

	struct nvme_prp_dma_pools *prp_pools = &dev->prp_pools[numa_node];

	size_t small_align = 256;



	if (prp_pools->small)

		return prp_pools; /* already initialized */



	prp_pools->large = dma_pool_create_node("prp list page", dev->dev,

						NVME_CTRL_PAGE_SIZE,

						NVME_CTRL_PAGE_SIZE, 0,

						numa_node);

	if (!prp_pools->large)

		return ERR_PTR(-ENOMEM);



	if (dev->ctrl.quirks & NVME_QUIRK_DMAPOOL_ALIGN_512)

		small_align = 512;



	/* Optimisation for I/Os between 4k and 128k */

	prp_pools->small = dma_pool_create_node("prp list 256", dev->dev,

						256, small_align, 0, numa_node);

	if (!prp_pools->small) {

		dma_pool_destroy(prp_pools->large);

		prp_pools->large = NULL;

		return ERR_PTR(-ENOMEM);

	}



	return prp_pools;

}



static void nvme_release_prp_pools(struct nvme_dev *dev)

{

	unsigned i;



	for (i = 0; i < nr_node_ids; i++) {

		struct nvme_prp_dma_pools *prp_pools = &dev->prp_pools[i];



		dma_pool_destroy(prp_pools->large);

		dma_pool_destroy(prp_pools->small);

	}

}



static int nvme_init_hctx_common(struct blk_mq_hw_ctx *hctx, void *data,

		unsigned qid)

{

	struct nvme_dev *dev = to_nvme_dev(data);

	struct nvme_queue *nvmeq = &dev->queues[qid];

	struct nvme_prp_dma_pools *prp_pools;

	struct blk_mq_tags *tags;



	tags = qid ? dev->tagset.tags[qid - 1] : dev->admin_tagset.tags[0];

	WARN_ON(tags != hctx->tags);

	prp_pools = nvme_setup_prp_pools(dev, hctx->numa_node);

	if (IS_ERR(prp_pools))

		return PTR_ERR(prp_pools);



	nvmeq->prp_pools = *prp_pools;

	hctx->driver_data = nvmeq;

	return 0;

}
@@ -539,7 +594,7 @@ static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req, 
	return true;

}



static void nvme_free_prps(struct nvme_dev *dev, struct request *req)

static void nvme_free_prps(struct nvme_queue *nvmeq, struct request *req)

{

	const int last_prp = NVME_CTRL_PAGE_SIZE / sizeof(__le64) - 1;

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -550,12 +605,13 @@ static void nvme_free_prps(struct nvme_dev *dev, struct request *req) 
		__le64 *prp_list = iod->list[i].prp_list;

		dma_addr_t next_dma_addr = le64_to_cpu(prp_list[last_prp]);



		dma_pool_free(dev->prp_page_pool, prp_list, dma_addr);

		dma_pool_free(nvmeq->prp_pools.large, prp_list, dma_addr);

		dma_addr = next_dma_addr;

	}

}



static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)

static void nvme_unmap_data(struct nvme_dev *dev, struct nvme_queue *nvmeq,

			    struct request *req)

{

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -570,13 +626,13 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req) 
	dma_unmap_sgtable(dev->dev, &iod->sgt, rq_dma_dir(req), 0);



	if (iod->nr_allocations == 0)

		dma_pool_free(dev->prp_small_pool, iod->list[0].sg_list,

		dma_pool_free(nvmeq->prp_pools.small, iod->list[0].sg_list,

			      iod->first_dma);

	else if (iod->nr_allocations == 1)

		dma_pool_free(dev->prp_page_pool, iod->list[0].sg_list,

		dma_pool_free(nvmeq->prp_pools.large, iod->list[0].sg_list,

			      iod->first_dma);

	else

		nvme_free_prps(dev, req);

		nvme_free_prps(nvmeq, req);

	mempool_free(iod->sgt.sgl, dev->iod_mempool);

}
@@ -594,7 +650,7 @@ static void nvme_print_sgl(struct scatterlist *sgl, int nents) 
	}

}



static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev,

static blk_status_t nvme_pci_setup_prps(struct nvme_queue *nvmeq,

		struct request *req, struct nvme_rw_command *cmnd)

{

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -630,10 +686,10 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev, 


	nprps = DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE);

	if (nprps <= (256 / 8)) {

		pool = dev->prp_small_pool;

		pool = nvmeq->prp_pools.small;

		iod->nr_allocations = 0;

	} else {

		pool = dev->prp_page_pool;

		pool = nvmeq->prp_pools.large;

		iod->nr_allocations = 1;

	}
@@ -675,7 +731,7 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev, 
	cmnd->dptr.prp2 = cpu_to_le64(iod->first_dma);

	return BLK_STS_OK;

free_prps:

	nvme_free_prps(dev, req);

	nvme_free_prps(nvmeq, req);

	return BLK_STS_RESOURCE;

bad_sgl:

	WARN(DO_ONCE(nvme_print_sgl, iod->sgt.sgl, iod->sgt.nents),
@@ -700,7 +756,7 @@ static void nvme_pci_sgl_set_seg(struct nvme_sgl_desc *sge, 
	sge->type = NVME_SGL_FMT_LAST_SEG_DESC << 4;

}



static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,

static blk_status_t nvme_pci_setup_sgls(struct nvme_queue *nvmeq,

		struct request *req, struct nvme_rw_command *cmd)

{

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -720,10 +776,10 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev, 
	}



	if (entries <= (256 / sizeof(struct nvme_sgl_desc))) {

		pool = dev->prp_small_pool;

		pool = nvmeq->prp_pools.small;

		iod->nr_allocations = 0;

	} else {

		pool = dev->prp_page_pool;

		pool = nvmeq->prp_pools.large;

		iod->nr_allocations = 1;

	}
@@ -787,12 +843,12 @@ static blk_status_t nvme_setup_sgl_simple(struct nvme_dev *dev, 
static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,

		struct nvme_command *cmnd)

{

	struct nvme_queue *nvmeq = req->mq_hctx->driver_data;

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);

	blk_status_t ret = BLK_STS_RESOURCE;

	int rc;



	if (blk_rq_nr_phys_segments(req) == 1) {

		struct nvme_queue *nvmeq = req->mq_hctx->driver_data;

		struct bio_vec bv = req_bvec(req);



		if (!is_pci_p2pdma_page(bv.bv_page)) {
@@ -827,9 +883,9 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, 
	}



	if (nvme_pci_use_sgls(dev, req, iod->sgt.nents))

		ret = nvme_pci_setup_sgls(dev, req, &cmnd->rw);

		ret = nvme_pci_setup_sgls(nvmeq, req, &cmnd->rw);

	else

		ret = nvme_pci_setup_prps(dev, req, &cmnd->rw);

		ret = nvme_pci_setup_prps(nvmeq, req, &cmnd->rw);

	if (ret != BLK_STS_OK)

		goto out_unmap_sg;

	return BLK_STS_OK;
@@ -844,6 +900,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, 
static blk_status_t nvme_pci_setup_meta_sgls(struct nvme_dev *dev,

					     struct request *req)

{

	struct nvme_queue *nvmeq = req->mq_hctx->driver_data;

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);

	struct nvme_rw_command *cmnd = &iod->cmd.rw;

	struct nvme_sgl_desc *sg_list;
@@ -867,7 +924,7 @@ static blk_status_t nvme_pci_setup_meta_sgls(struct nvme_dev *dev, 
	if (rc)

		goto out_free_sg;



	sg_list = dma_pool_alloc(dev->prp_small_pool, GFP_ATOMIC, &sgl_dma);

	sg_list = dma_pool_alloc(nvmeq->prp_pools.small, GFP_ATOMIC, &sgl_dma);

	if (!sg_list)

		goto out_unmap_sg;
@@ -949,7 +1006,7 @@ static blk_status_t nvme_prep_rq(struct nvme_dev *dev, struct request *req) 
	return BLK_STS_OK;

out_unmap_data:

	if (blk_rq_nr_phys_segments(req))

		nvme_unmap_data(dev, req);

		nvme_unmap_data(dev, req->mq_hctx->driver_data, req);

out_free_cmd:

	nvme_cleanup_cmd(req);

	return ret;
@@ -1039,6 +1096,7 @@ static void nvme_queue_rqs(struct rq_list *rqlist) 
}



static __always_inline void nvme_unmap_metadata(struct nvme_dev *dev,

						struct nvme_queue *nvmeq,

						struct request *req)

{

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -1050,7 +1108,7 @@ static __always_inline void nvme_unmap_metadata(struct nvme_dev *dev, 
		return;

	}



	dma_pool_free(dev->prp_small_pool, iod->meta_list.sg_list,

	dma_pool_free(nvmeq->prp_pools.small, iod->meta_list.sg_list,

		      iod->meta_dma);

	dma_unmap_sgtable(dev->dev, &iod->meta_sgt, rq_dma_dir(req), 0);

	mempool_free(iod->meta_sgt.sgl, dev->iod_meta_mempool);
@@ -1062,10 +1120,10 @@ static __always_inline void nvme_pci_unmap_rq(struct request *req) 
	struct nvme_dev *dev = nvmeq->dev;



	if (blk_integrity_rq(req))

		nvme_unmap_metadata(dev, req);

		nvme_unmap_metadata(dev, nvmeq, req);



	if (blk_rq_nr_phys_segments(req))

		nvme_unmap_data(dev, req);

		nvme_unmap_data(dev, nvmeq, req);

}



static void nvme_pci_complete_rq(struct request *req)
@@ -2842,35 +2900,6 @@ static int nvme_disable_prepare_reset(struct nvme_dev *dev, bool shutdown) 
	return 0;

}



static int nvme_setup_prp_pools(struct nvme_dev *dev)

{

	size_t small_align = 256;



	dev->prp_page_pool = dma_pool_create("prp list page", dev->dev,

						NVME_CTRL_PAGE_SIZE,

						NVME_CTRL_PAGE_SIZE, 0);

	if (!dev->prp_page_pool)

		return -ENOMEM;



	if (dev->ctrl.quirks & NVME_QUIRK_DMAPOOL_ALIGN_512)

		small_align = 512;



	/* Optimisation for I/Os between 4k and 128k */

	dev->prp_small_pool = dma_pool_create("prp list 256", dev->dev,

						256, small_align, 0);

	if (!dev->prp_small_pool) {

		dma_pool_destroy(dev->prp_page_pool);

		return -ENOMEM;

	}

	return 0;

}



static void nvme_release_prp_pools(struct nvme_dev *dev)

{

	dma_pool_destroy(dev->prp_page_pool);

	dma_pool_destroy(dev->prp_small_pool);

}



static int nvme_pci_alloc_iod_mempool(struct nvme_dev *dev)

{

	size_t meta_size = sizeof(struct scatterlist) * (NVME_MAX_META_SEGS + 1);
@@ -3185,7 +3214,8 @@ static struct nvme_dev *nvme_pci_alloc_dev(struct pci_dev *pdev, 
	struct nvme_dev *dev;

	int ret = -ENOMEM;



	dev = kzalloc_node(sizeof(*dev), GFP_KERNEL, node);

	dev = kzalloc_node(sizeof(*dev) + nr_node_ids * sizeof(*dev->prp_pools),

			   GFP_KERNEL, node);

	if (!dev)

		return ERR_PTR(-ENOMEM);

	INIT_WORK(&dev->ctrl.reset_work, nvme_reset_work);
@@ -3260,13 +3290,9 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id) 
	if (result)

		goto out_uninit_ctrl;



	result = nvme_setup_prp_pools(dev);

	if (result)

		goto out_dev_unmap;



	result = nvme_pci_alloc_iod_mempool(dev);

	if (result)

		goto out_release_prp_pools;

		goto out_dev_unmap;



	dev_info(dev->ctrl.device, "pci function %s\n", dev_name(&pdev->dev));
@@ -3342,8 +3368,6 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id) 
out_release_iod_mempool:

	mempool_destroy(dev->iod_mempool);

	mempool_destroy(dev->iod_meta_mempool);

out_release_prp_pools:

	nvme_release_prp_pools(dev);

out_dev_unmap:

	nvme_dev_unmap(dev);

out_uninit_ctrl: