Linux-NVME Archive on lore.kernel.org
 help / color / Atom feed
From: Israel Rukshin <israelr@mellanox.com>
To: Linux-nvme <linux-nvme@lists.infradead.org>,
	Sagi Grimberg <sagi@grimberg.me>, Christoph Hellwig <hch@lst.de>,
	James Smart <jsmart2021@gmail.com>,
	Keith Busch <kbusch@kernel.org>
Cc: Israel Rukshin <israelr@mellanox.com>, Max Gurtovoy <maxg@mellanox.com>
Subject: [PATCH 2/3] nvme-fc: Avoid preallocating big SGL for data
Date: Sun, 24 Nov 2019 18:38:31 +0200
Message-ID: <1574613512-5943-3-git-send-email-israelr@mellanox.com> (raw)
In-Reply-To: <1574613512-5943-1-git-send-email-israelr@mellanox.com>

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.

Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.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 679a721..13cb00e 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 @@ enum {
 	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 @@ enum {
 	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 @@ enum {
 	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;
 }
-- 
1.8.3.1


_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-24 16:38 [PATCH 0/3] nvme: " Israel Rukshin
2019-11-24 16:38 ` [PATCH 1/3] nvme-rdma: " Israel Rukshin
2019-11-26 16:53   ` Christoph Hellwig
2019-11-24 16:38 ` Israel Rukshin [this message]
2019-11-25 17:04   ` [PATCH 2/3] nvme-fc: " James Smart
2019-11-24 16:38 ` [PATCH 3/3] nvmet-loop: " Israel Rukshin
2019-11-25  2:24   ` Chaitanya Kulkarni
2019-11-26 16:53   ` Christoph Hellwig
2019-11-26 17:40   ` Keith Busch

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1574613512-5943-3-git-send-email-israelr@mellanox.com \
    --to=israelr@mellanox.com \
    --cc=hch@lst.de \
    --cc=jsmart2021@gmail.com \
    --cc=kbusch@kernel.org \
    --cc=linux-nvme@lists.infradead.org \
    --cc=maxg@mellanox.com \
    --cc=sagi@grimberg.me \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NVME Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvme/0 linux-nvme/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nvme linux-nvme/ https://lore.kernel.org/linux-nvme \
		linux-nvme@lists.infradead.org
	public-inbox-index linux-nvme

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-nvme


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git