On Thu, Feb 21, 2019 at 6:48 PM Jens Axboe [off-list ref] wrote:

On 2/21/19 5:10 AM, Marek Majkowski wrote:

quoted

quoted

From: Jens Axboe <axboe@kernel.dk>
Subject: [PATCHSET v15] io_uring IO interface
Message-ID: [ref] (raw)

Some final tweaks, mostly cosmetic, but also two important fixes:

1) Ensure that we account the skb appropriately against the socket.
   Some network config options apparently return is an skb with
   ->truesize != 0 when allocated with a size of 0, ensure we add
   those as references against sock->sk_wmem_alloc. Reported by
   Matt Mullins.

Jens,

I tried using io_uring with network sockets. It seem to be doing the
right thing. One bit is missing though: "flags" as in recv(2).

In perfect world I would like to specify at least:
 - MSG_DONTWAIT
 - MSG_WAITALL
 - MSG_NOSIGNAL

Right now, unless I'm missing something, io_uring_sqe doesn't have a
place where we could store these. "flags" is needed for any
non-trivial network I/O.

We have flags for sqes, depending on the type. You can add to the
union that already holds rw_flags/fsync_flags/poll_events? There's
also a (smaller) flags field that applies for all types, which
currently only holds the fixed file flag.

The "sqe->flags" right now is used by the IOSQE_FIXED_FILE which has
the same value as MSG_OOB.

Sticking recv/send flags into the "rw_flags" union perhaps could work,
barring the discussion about naming. The obvious names don't make
sense. recv_flags, send_flags or socket_flags don't sound right.

If we tried to add networking stuff to io_uring (for batchinig and async), then:
 - send()/recv() could work, only needs the "flags" field
 - sendmsg()/recvmsg() likewise
 - sendto()/recvfrom() require two more pointers: (struct sockaddr
*dest_addr, socklen_t addrlen)
 - sendmmsg() / recvmmsg() are perhaps irrelevant

Non-blocking stuff like socket(), setsockopt(), bind() perhaps don't
need to be considered, although could benefit from batching.

Not sure what to think about connect() and accept(). In the
prehistoric days there seem to have been an attempt to add socket
things to libaio struct iocb. See:

https://code.woboq.org/linux/include/libaio.h.html#iocb::(anonymous)::saddr

struct iocb {
    ...
    union {
        ...
        struct io_iocb_sockaddr    saddr;
    } u;
};

Are there chances of reserving space for two pointers in io_uring_sqe,
which could be used for sendto/recvfrom/accept if we decided to add
more network support?

Cheers,
    Marek

If you're talking on a per-syscall type of flag, io_uring_enter(2)
does take a flags member.

--
Jens Axboe

--
To unsubscribe, send a message with 'unsubscribe linux-aio' in
the body to majordomo@kvack.org.  For more info on Linux AIO,
see: http://www.kvack.org/aio/
Don't email: <a href=mailto:"aart@kvack.org">aart@kvack.org</a>