[PATCHSET,RFC,0/3] Add support for ring resizing

Message

Jens Axboe Oct. 22, 2024, 2:08 a.m. UTC

Hi,

Something that's come up several times over the years is how to deal
with ring sizing. The SQ ring sizing is usually trivial - it just
controls the batch submit size, and usually it's not that difficult
to just submit if the app fails to get a free SQE.

For the CQ ring, it's a different story. For networked workloads, it
can be hard to appropriately size the CQ ring without knowing exactly
how busy a given ring will be. This leads to applications grossly
over-sizing the ring, just in case, which is wasteful.

Here's a stab at supporting ring resizing. It supports resizing of
both rings, SQ and CQ, as it's really no different than just doing
the CQ ring itself. liburing has a 'resize-rings' branch with a bit
of support code, and a test case:

https://git.kernel.dk/cgit/liburing/log/?h=resize-rings

and these patches can also be found here:

https://git.kernel.dk/cgit/linux/log/?h=io_uring-ring-resize

 include/uapi/linux/io_uring.h |   3 +
 io_uring/io_uring.c           |  84 ++++++++++--------
 io_uring/io_uring.h           |   6 ++
 io_uring/register.c           | 161 ++++++++++++++++++++++++++++++++++
 4 files changed, 216 insertions(+), 38 deletions(-)