From b1ae1a238900474a9f51431c0f7f169ade1faa19 Mon Sep 17 00:00:00 2001 From: Israel Rukshin Date: Sun, 24 Nov 2019 18:38:31 +0200 Subject: [PATCH] nvme-fc: Avoid preallocating big SGL for data nvme_fc_create_io_queues() preallocates a big buffer for the IO SGL based on SG_CHUNK_SIZE. Modern DMA engines are often capable of dealing with very big segments so the SG_CHUNK_SIZE is often too big. SG_CHUNK_SIZE results in a static 4KB SGL allocation per command. If a controller has lots of deep queues, preallocation for the sg list can consume substantial amounts of memory. For nvme-fc, nr_hw_queues can be 128 and each queue's depth 128. This means the resulting preallocation for the data SGL is 128*128*4K = 64MB per controller. Switch to runtime allocation for SGL for lists longer than 2 entries. This is the approach used by NVMe PCI so it should be reasonable for NVMeOF as well. Runtime SGL allocation has always been the case for the legacy I/O path so this is nothing new. Reviewed-by: Max Gurtovoy Reviewed-by: James Smart Signed-off-by: Israel Rukshin Signed-off-by: Keith Busch --- drivers/nvme/host/fc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c index 679a721ae229..13cb00e56cac 100644 --- a/drivers/nvme/host/fc.c +++ b/drivers/nvme/host/fc.c @@ -95,7 +95,7 @@ struct nvme_fc_fcp_op { struct nvme_fcp_op_w_sgl { struct nvme_fc_fcp_op op; - struct scatterlist sgl[SG_CHUNK_SIZE]; + struct scatterlist sgl[NVME_INLINE_SG_CNT]; uint8_t priv[0]; }; @@ -2141,7 +2141,7 @@ nvme_fc_map_data(struct nvme_fc_ctrl *ctrl, struct request *rq, freq->sg_table.sgl = freq->first_sgl; ret = sg_alloc_table_chained(&freq->sg_table, blk_rq_nr_phys_segments(rq), freq->sg_table.sgl, - SG_CHUNK_SIZE); + NVME_INLINE_SG_CNT); if (ret) return -ENOMEM; @@ -2150,7 +2150,7 @@ nvme_fc_map_data(struct nvme_fc_ctrl *ctrl, struct request *rq, freq->sg_cnt = fc_dma_map_sg(ctrl->lport->dev, freq->sg_table.sgl, op->nents, rq_dma_dir(rq)); if (unlikely(freq->sg_cnt <= 0)) { - sg_free_table_chained(&freq->sg_table, SG_CHUNK_SIZE); + sg_free_table_chained(&freq->sg_table, NVME_INLINE_SG_CNT); freq->sg_cnt = 0; return -EFAULT; } @@ -2173,7 +2173,7 @@ nvme_fc_unmap_data(struct nvme_fc_ctrl *ctrl, struct request *rq, fc_dma_unmap_sg(ctrl->lport->dev, freq->sg_table.sgl, op->nents, rq_dma_dir(rq)); - sg_free_table_chained(&freq->sg_table, SG_CHUNK_SIZE); + sg_free_table_chained(&freq->sg_table, NVME_INLINE_SG_CNT); freq->sg_cnt = 0; }