RDMA/mlx5: Improve PI handover performance
In some loads, there is performance degradation when using KLM mkey
instead of MTT mkey. This is because KLM descriptor access is via
indirection that might require more HW resources and cycles.
Using KLM descriptor is not necessary when there are no gaps at the
data/metadata sg lists. As an optimization, use MTT mkey whenever it
is possible. For that matter, allocate internal MTT mkey and choose the
effective pi_mr for in transaction according to the required mapping
scheme.
The setup of the tested benchmark (using iSER ULP):
- 2 servers with 24 cores (1 initiator and 1 target)
- ConnectX-4/ConnectX-5 adapters
- 24 target sessions with 1 LUN each
- ramdisk backstore
- PI active
Performance results running fio (24 jobs, 128 iodepth) using
write_generate=1 and read_verify=1 (w/w.o/baseline):
bs IOPS(read) IOPS(write)
---- ---------- ----------
512 1262.4K/1243.3K/1147.1K 1732.1K/1725.1K/1423.8K
4k 570902/571233/457874 773982/743293/642080
32k 72086/72388/71933 96164/71789/93249
Using write_generate=0 and read_verify=0 (w/w.o patch):
bs IOPS(read) IOPS(write)
---- ---------- ----------
512 1600.1K/1572.1K/1393.3K 1830.3K/1823.5K/1557.2K
4k 937272/921992/762934 815304/753772/646071
32k 77369/75052/72058 97435/73180/94612
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Suggested-by: Max Gurtovoy <maxg@mellanox.com>
Suggested-by: Idan Burstein <idanb@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
3 files changed