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nvmet-loop: Avoid preallocating big SGL for data
nvme_loop_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 nvmet-loop, 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. Tested-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Reviewed-by: Max Gurtovoy <maxg@mellanox.com> Signed-off-by: Israel Rukshin <israelr@mellanox.com> Signed-off-by: Keith Busch <kbusch@kernel.org>
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1 changed files with 4 additions and 4 deletions
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@ -76,7 +76,7 @@ static void nvme_loop_complete_rq(struct request *req)
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{
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{
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struct nvme_loop_iod *iod = blk_mq_rq_to_pdu(req);
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struct nvme_loop_iod *iod = blk_mq_rq_to_pdu(req);
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sg_free_table_chained(&iod->sg_table, SG_CHUNK_SIZE);
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sg_free_table_chained(&iod->sg_table, NVME_INLINE_SG_CNT);
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nvme_complete_rq(req);
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nvme_complete_rq(req);
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}
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}
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@ -156,7 +156,7 @@ static blk_status_t nvme_loop_queue_rq(struct blk_mq_hw_ctx *hctx,
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iod->sg_table.sgl = iod->first_sgl;
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iod->sg_table.sgl = iod->first_sgl;
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if (sg_alloc_table_chained(&iod->sg_table,
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if (sg_alloc_table_chained(&iod->sg_table,
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blk_rq_nr_phys_segments(req),
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blk_rq_nr_phys_segments(req),
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iod->sg_table.sgl, SG_CHUNK_SIZE)) {
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iod->sg_table.sgl, NVME_INLINE_SG_CNT)) {
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nvme_cleanup_cmd(req);
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nvme_cleanup_cmd(req);
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return BLK_STS_RESOURCE;
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return BLK_STS_RESOURCE;
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}
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}
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@ -342,7 +342,7 @@ static int nvme_loop_configure_admin_queue(struct nvme_loop_ctrl *ctrl)
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ctrl->admin_tag_set.reserved_tags = 2; /* connect + keep-alive */
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ctrl->admin_tag_set.reserved_tags = 2; /* connect + keep-alive */
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ctrl->admin_tag_set.numa_node = NUMA_NO_NODE;
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ctrl->admin_tag_set.numa_node = NUMA_NO_NODE;
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ctrl->admin_tag_set.cmd_size = sizeof(struct nvme_loop_iod) +
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ctrl->admin_tag_set.cmd_size = sizeof(struct nvme_loop_iod) +
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SG_CHUNK_SIZE * sizeof(struct scatterlist);
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NVME_INLINE_SG_CNT * sizeof(struct scatterlist);
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ctrl->admin_tag_set.driver_data = ctrl;
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ctrl->admin_tag_set.driver_data = ctrl;
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ctrl->admin_tag_set.nr_hw_queues = 1;
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ctrl->admin_tag_set.nr_hw_queues = 1;
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ctrl->admin_tag_set.timeout = ADMIN_TIMEOUT;
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ctrl->admin_tag_set.timeout = ADMIN_TIMEOUT;
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@ -516,7 +516,7 @@ static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)
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ctrl->tag_set.numa_node = NUMA_NO_NODE;
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ctrl->tag_set.numa_node = NUMA_NO_NODE;
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ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
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ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
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ctrl->tag_set.cmd_size = sizeof(struct nvme_loop_iod) +
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ctrl->tag_set.cmd_size = sizeof(struct nvme_loop_iod) +
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SG_CHUNK_SIZE * sizeof(struct scatterlist);
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NVME_INLINE_SG_CNT * sizeof(struct scatterlist);
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ctrl->tag_set.driver_data = ctrl;
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ctrl->tag_set.driver_data = ctrl;
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ctrl->tag_set.nr_hw_queues = ctrl->ctrl.queue_count - 1;
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ctrl->tag_set.nr_hw_queues = ctrl->ctrl.queue_count - 1;
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ctrl->tag_set.timeout = NVME_IO_TIMEOUT;
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ctrl->tag_set.timeout = NVME_IO_TIMEOUT;
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