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
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