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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> |
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