On Fri, Jul 24, 2026 at 02:21:15PM -0700, Bobby Eshleman wrote: > From: Bobby Eshleman <[email protected]> > > Every devmem dmabuf binding today hands the page_pool PAGE_SIZE niovs. > This caps a single RX descriptor at PAGE_SIZE, burning CPU on buffer > churn for large flows. > > Add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_PAGE_SIZE, that > lets userspace request a larger niov size. The value must be a power of > two >= PAGE_SIZE. > > Measurements: > Setup: kperf in devmem RX/TX cuda mode, 4 flows, 64 MB messages, 60s, > dctcp, num-rx-queues=4, dmabuf-rx/tx-size-mb=2048, 10 runs per niov > size, mlx5. > > CPU Util: > > niov net sirq % net idle % app sys % app idle > % > ----- ---------------- ---------------- ---------------- > ---------------- > 4K 62.38 +/- 8.27 33.40 +/- 7.51 54.15 +/- 10.23 43.67 +/- > 10.53 > 16K 58.91 +/- 5.35 35.23 +/- 5.88 41.05 +/- 8.87 56.42 +/- > 9.24 > 32K 64.12 +/- 0.68 31.09 +/- 1.48 44.54 +/- 3.51 52.63 +/- > 3.65 > 64K 54.69 +/- 5.54 39.67 +/- 5.81 35.47 +/- 3.11 61.97 +/- > 3.27 > > RX app sys % drops ~19% from 4K to 64K. > > Throughput: > > niov RX dev Gbps RX flow avg Gbps > ----- ---------------- ----------------- > 4K 300.63 +/- 53.21 75.16 +/- 13.30 > 16K 321.35 +/- 28.20 80.34 +/- 7.05 > 32K 347.63 +/- 2.20 86.91 +/- 0.55 > 64K 332.11 +/- 14.26 83.03 +/- 3.56 > > Throughput seems to increase, but the stdev is pretty wide so could just > be noise. > > kperf support (not yet merged): > https://github.com/facebookexperimental/kperf/commit/8837577f920876bce6986ec18869ac04439ebcd2 > > Signed-off-by: Bobby Eshleman <[email protected]> > Acked-by: Stanislav Fomichev <[email protected]> > Reviewed-by: Mina Almasry <[email protected]> > --- > Documentation/netlink/specs/netdev.yaml | 17 ++++++++++++ > include/uapi/linux/netdev.h | 1 + > net/core/devmem.c | 49 > +++++++++++++++++++-------------- > net/core/devmem.h | 13 ++++++--- > net/core/netdev-genl-gen.c | 11 ++++++-- > net/core/netdev-genl-gen.h | 1 + > net/core/netdev-genl.c | 18 ++++++++++-- > tools/include/uapi/linux/netdev.h | 1 + > 8 files changed, 83 insertions(+), 28 deletions(-) >
LGTM, Reviewed-by: Nikolay Aleksandrov <[email protected]> Cheers, Nik
