[RFC v3 0/9] fixed worker

[Hao Xu]

This is the third version of fixed worker implementation.
Wrote a nop test program to test it, 3 fixed-workers VS 3 normal workers.
normal workers:
./run_nop_wqe.sh nop_wqe_normal 200000 100 3 1-3
        time spent: 10464397 usecs      IOPS: 1911242
        time spent: 9610976 usecs       IOPS: 2080954
        time spent: 9807361 usecs       IOPS: 2039284

fixed workers:
./run_nop_wqe.sh nop_wqe_fixed 200000 100 3 1-3
        time spent: 17314274 usecs      IOPS: 1155116
        time spent: 17016942 usecs      IOPS: 1175299
        time spent: 17908684 usecs      IOPS: 1116776

About 2x improvement. From perf result, almost no acct->lock contension.
Test program: https://github.com/HowHsu/liburing/tree/fixed_worker
liburing/test/nop_wqe.c

v2->v3:
 - change dispatch work strategy from random to round-robin

things to be done:
 - Still need some thinking about the work cancellation
 - not very sure IO_WORKER_F_EXIT is safe enough on synchronization
 - the iowq hash stuff is not compatible with fixed worker for now

Any comments are welcome. Thanks in advance.

Hao Xu (9):
  io-wq: add a worker flag for individual exit
  io-wq: change argument of create_io_worker() for convienence
  io-wq: add infra data structure for fixed workers
  io-wq: tweak io_get_acct()
  io-wq: fixed worker initialization
  io-wq: fixed worker exit
  io-wq: implement fixed worker logic
  io-wq: batch the handling of fixed worker private works
  io_uring: add register fixed worker interface

 fs/io-wq.c                    | 460 ++++++++++++++++++++++++++++++----
 fs/io-wq.h                    |   8 +
 fs/io_uring.c                 |  71 ++++++
 include/uapi/linux/io_uring.h |  11 +
 4 files changed, 501 insertions(+), 49 deletions(-)

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2.36.0