From: Israel Rukshin <israelr@mellanox.com>
Date: Sun, 24 Nov 2019 18:38:31 +0200
Subject: [PATCH] nvme-fc: Avoid preallocating big SGL for data
Git-commit: b1ae1a238900474a9f51431c0f7f169ade1faa19
Patch-mainline: v5.5-rc2
References: bsc#1169045
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>
Acked-by: Hannes Reinecke <hare@suse.com>
---
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;
}
--
2.16.4