warning: not properly tested Follow up on the discussion about optimising copy_from_user() for read/write attributes. The idea here is to use registered regions (see IORING_REGISTER_MEM_REGION) for that purpose pretty much in the same way registered wait arguments work. Putting it simply, a region is a user provided chunk of memory that has been registered and pre-mapped into io_uring / kernel, but it has more modes like mmap'ing kernel memory. For attributes the user passes an offset into a region, and the kernel can read from it directly without copy_from_user(). The other alternative is to store attributes into the upper half of SQE128, but then we might run out of space in SQE for larger and/or compound attributes. It'd also require SQE128, which has a (perhaps minor) downside when other types of requests don't need it. Pavel Begunkov (4): io_uring: add structure for registered arguments io_uring: add registered request arguments io_uring/rw: use READ_ONCE with rw attributes io_uring/rw: pre-mapped rw attributes include/linux/io_uring_types.h | 11 ++++++++-- include/uapi/linux/io_uring.h | 4 +++- io_uring/io_uring.c | 23 +++------------------ io_uring/io_uring.h | 16 +++++++++++++++ io_uring/register.c | 7 +++++-- io_uring/rw.c | 37 ++++++++++++++++++++++++---------- 6 files changed, 62 insertions(+), 36 deletions(-) -- 2.47.1
