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author | Israel Rukshin <israelr@mellanox.com> | 2019-11-24 18:38:31 +0200 |
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committer | Keith Busch <kbusch@kernel.org> | 2019-11-27 02:14:01 +0900 |
commit | b1ae1a238900474a9f51431c0f7f169ade1faa19 (patch) | |
tree | 64451d3a747ecfe0e757d5a49b2f29953a1680d2 /scripts/tracing | |
parent | 38e1800275d3af607e4df92ff49dc2cf442586a4 (diff) |
nvme-fc: Avoid preallocating big SGL for data
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>
Diffstat (limited to 'scripts/tracing')
0 files changed, 0 insertions, 0 deletions