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