Hi folks, I'm setting up an MPICH over libfabric over psm2 for MareNostrum (Omni-Path), to try out some ideas. I've compiled libfabric 1.5 (last one that compiles in this machine) over opa-psm2-11.2.185, and mpich-3.4.2 + mpich-4.0a1 in both ch3 and ch4 (yes 4 MPICH variants). There's only psm2 support in libfabric, so no danger of falling back to other providers. ldd confirms my libfabric is linked. ./fi_info     provider: psm2     fabric: psm2     domain: psm2     version: 1.5     type: FI_EP_RDM     protocol: FI_PROTO_PSMX2 I'm comparing 2-node pt2pt performance against impi/2017.4 using osu microbenchmarks. While both fi_pingong and impi give me a max. BW of ~10 MB/s, all mpich versions stick at ~3 MB/s. Is this expected? I mean, is there so much secret sauce in impi? Or, am likely doing something wrong? I'm doing fairly plain configures, nothing fancy, e.g.:   ./configure --prefix=... --with-device=ch4:ofi --with-libfabric=... I'd appreciate some guidance  - my MPICH tweaking is a little rusted :) Best,   Toni