[PATCH 0/3] optimise submit+iopoll mutex locking

[Pavel Begunkov <asml.silence@gmail.com>]

This saves one mutex lock/unlock pair per syscall when users do
submit + getevents. Perf tells that for QD1 iopoll this patch reduces overhead
on locking from ~4.3% to ~2.6%, iow cuts 1.3% - 1.9% of CPU time. Something
similar I see in final throughput.

It's a good win for smaller QD, especially considering that io_uring only
takes about 20-30% of all cycles, the rest goes to syscalling, the block
layer and below.

Pavel Begunkov (3):
  io_uring: split off IOPOLL argument verifiction
  io_uring: pre-calculate syscall iopolling decision
  io_uring: optimise mutex locking for submit+iopoll

 fs/io_uring.c | 86 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 56 insertions(+), 30 deletions(-)

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2.35.1