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 0/3] nvme: Avoid preallocating big SGL for data
Date: Sun, 24 Nov 2019 18:38:29 +0200 [thread overview]
Message-ID: <1574613512-5943-1-git-send-email-israelr@mellanox.com> (raw)
When nvme allocates a tagset it 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. 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.
The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't
support SG_CHAIN, use only runtime allocation for the SGL.
Israel Rukshin (3):
nvme-rdma: Avoid preallocating big SGL for data
nvme-fc: Avoid preallocating big SGL for data
nvmet-loop: Avoid preallocating big SGL for data
drivers/nvme/host/fc.c | 8 ++++----
drivers/nvme/host/nvme.h | 6 ++++++
drivers/nvme/host/rdma.c | 10 +++++-----
drivers/nvme/target/loop.c | 8 ++++----
4 files changed, 19 insertions(+), 13 deletions(-)
--
1.8.3.1
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next reply other threads:[~2019-11-24 16:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-24 16:38 Israel Rukshin [this message]
2019-11-24 16:38 ` [PATCH 1/3] nvme-rdma: Avoid preallocating big SGL for data Israel Rukshin
2019-11-26 16:53 ` Christoph Hellwig
2019-11-24 16:38 ` [PATCH 2/3] nvme-fc: " Israel Rukshin
2019-11-25 17:04 ` 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
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