On Wed, Nov 19, 2025 at 07:37:07PM -0800, Bobby Eshleman wrote: > This series improves the CPU cost of RX token management by adding an > attribute to NETDEV_CMD_BIND_RX that configures sockets using the > binding to avoid the xarray allocator and instead use a per-binding niov > array and a uref field in niov. > > Improvement is ~13% cpu util per RX user thread. > > Using kperf, the following results were observed: > > Before: > Average RX worker idle %: 13.13, flows 4, test runs 11 > After: > Average RX worker idle %: 26.32, flows 4, test runs 11 > > Two other approaches were tested, but with no improvement. Namely, 1) > using a hashmap for tokens and 2) keeping an xarray of atomic counters > but using RCU so that the hotpath could be mostly lockless. Neither of > these approaches proved better than the simple array in terms of CPU. > > The attribute NETDEV_A_DMABUF_AUTORELEASE is added to toggle the > optimization. It is an optional attribute and defaults to 0 (i.e., > optimization on). >
[...] > > Changes in v7: > - use netlink instead of sockopt (Stan) > - restrict system to only one mode, dmabuf bindings can not co-exist > with different modes (Stan) > - use static branching to enforce single system-wide mode (Stan) > - Link to v6: > https://lore.kernel.org/r/20251104-scratch-bobbyeshleman-devmem-tcp-token-upstream-v6-0-ea98cf4d4...@meta.com > Mina, I was wondering if you had any feedback on this approach? Best, Bobby
