... >>> >>> To fix this issue, export cq overflow status to userspace, then >>> helper functions() in liburing, such as io_uring_peek_cqe, can be >>> aware of this cq overflow and do flush accordingly. >> >> Is there any way we can accomplish the same without exporting >> another set of flags? Would it be enough for the SQPOLl thread to set >> IORING_SQ_NEED_WAKEUP if we're in overflow condition? That should >> result in the app entering the kernel when it's flushed the user CQ >> side, and then the sqthread could attempt to flush the pending >> events as well. >> >> Something like this, totally untested... > > OK, took a closer look at this, it's a generic thing, not just > SQPOLL related. My bad! > > Anyway, my suggestion would be to add IORING_SQ_CQ_OVERFLOW to the > existing flags, and then make a liburing change almost identical to > what you had. How about CQ being full as an indicator that flush is required? With a properly set CQ size there shouldn't be much false positives. -- Pavel Begunkov
