Hi Pavel,

>>>  static int io_sendmsg_copy_hdr(struct io_kiocb *req,
>>>  			       struct io_async_msghdr *iomsg)
>>>  {
>>> -	iomsg->iov = iomsg->fast_iov;
>>>  	iomsg->msg.msg_name = &iomsg->addr;
>>> +	iomsg->free_iov = iomsg->fast_iov;
>>
>> Why this? Isn't the idea of this patch that free_iov is never == fast_iov?
> 
> That's a part of __import_iovec() and sendmsg_copy_msghdr() API, you pass
> fast_iov as such and get back NULL or a newly allocated one in it.
I think that should at least get a comment to make this clear and
maybe a temporary variable like this:

tmp_iov = iomsg->fast_iov;
__import_iovec(..., &tmp_iov, ...);
iomsg->free_iov = tmp_iov;

>>> @@ -4872,8 +4867,8 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
>>>  
>>>  	if (req->flags & REQ_F_BUFFER_SELECTED)
>>>  		cflags = io_put_recv_kbuf(req);
>>> -	if (kmsg->iov != kmsg->fast_iov)
>>> -		kfree(kmsg->iov);
>>> +	if (kmsg->free_iov)
>>> +		kfree(kmsg->free_iov);
>>
>> kfree() handles NULL, or is this a hot path and we want to avoid a function call?
> 
> Yes, the hot path here is not having iov allocated, and Jens told before
> that he had observed overhead for a similar place in io_[read,write].

Ok, a comment would also help here...

metze