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| author | Israel Rukshin <israelr@mellanox.com> | 2019-11-24 18:38:31 +0200 |
|---|---|---|
| committer | Keith Busch <kbusch@kernel.org> | 2019-11-27 02:14:01 +0900 |
| commit | b1ae1a238900474a9f51431c0f7f169ade1faa19 (patch) | |
| tree | 64451d3a747ecfe0e757d5a49b2f29953a1680d2 /drivers/nvme/host/fc.c | |
| parent | 38e1800275d3af607e4df92ff49dc2cf442586a4 (diff) | |
| download | lwn-b1ae1a238900474a9f51431c0f7f169ade1faa19.tar.gz lwn-b1ae1a238900474a9f51431c0f7f169ade1faa19.zip | |
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 <maxg@mellanox.com>
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Diffstat (limited to 'drivers/nvme/host/fc.c')
| -rw-r--r-- | drivers/nvme/host/fc.c | 8 |
1 files 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; } |