Re: Emulating epoll

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

On 4/20/21 6:48 PM, Jesse Hughes wrote:
> Awesome, thanks for the info and your hard work Pavel!

fwiw, there are also specialised send[msg],recv[msg] requests
supported, not only read/write, see IORING_OP_* opcodes

> 
> On 4/20/21 5:37 PM, Jesse Hughes wrote:
>> Hello,
>>
>> I want to start by saying thank-you for working on io_uring.  My experience using it thus far has been great.
>>
>> I'm working on an open-source database product (KeyDB, a multi-threaded redis fork) and we're considering rewriting our IO to use io_uring.  Our current implementation uses epoll, and processes IO on (mainly) sockets as they become ready.
> 
> Wonderful, always interesting to learn about emerging use cases
> and new apps using it.
> 
>>
>> If I'm understanding the literature correctly, to emulate epoll, we should be able to set up a uring, put in a read sqe for each incoming socket connection, then (using liburing) call io_uring_wait_sqe​.  Correct?  Is there a better way of doing that?
> 
> In general, the best way to do I/O is to issue a read/write/etc. sqe
> directly as you've mentioned. io_uring will take care of doing polling
> internally or finding a better way to execute it.
> 
> However, to simply emulate epoll IORING_OP_POLL_ADD requests can be
> used There is support for multi-shot poll requests, which Jens added
> for coming linux 5.13
> 
>>
>> Our end-goal is not to emulate epoll, but that seems like the quickest way of getting something working that we can do further experiments with.
>>
>> For reference, if anyone's interested, our source repo is at : https://github.com/EQ-Alpha/KeyDB

-- 
Pavel Begunkov