Re: [PATCH] SUNRPC: Remove rpc_xprt::tsh_size

[Trond Myklebust <trondmy@hammerspace.com>]

On Thu, 2019-01-03 at 13:29 -0500, Chuck Lever wrote:
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index d5ce1a8..66b08aa 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -678,6 +678,31 @@ static void xs_stream_data_receive_workfn(struct
> work_struct *work)
>  
>  #define XS_SENDMSG_FLAGS	(MSG_DONTWAIT | MSG_NOSIGNAL)
>  
> +static int xs_send_record_marker(struct sock_xprt *transport,
> +				 const struct rpc_rqst *req)
> +{
> +	static struct msghdr msg = {
> +		.msg_name	= NULL,
> +		.msg_namelen	= 0,
> +		.msg_flags	= (XS_SENDMSG_FLAGS | MSG_MORE),
> +	};
> +	rpc_fraghdr marker;
> +	struct kvec iov = {
> +		.iov_base	= &marker,
> +		.iov_len	= sizeof(marker),
> +	};
> +	u32 reclen;
> +
> +	if (unlikely(!transport->sock))
> +		return -ENOTSOCK;
> +	if (req->rq_bytes_sent)
> +		return 0;

The test needs to use transport->xmit.offset, not req->rq_bytes_sent
You also need to update transport->xmit.offset on success, and be
prepared to handle the case where < sizeof(marker) bytes get
transmitted due to a write_space condition.

> +
> +	reclen = req->rq_snd_buf.len;
> +	marker = cpu_to_be32(RPC_LAST_STREAM_FRAGMENT | reclen);
> +	return kernel_sendmsg(transport->sock, &msg, &iov, 1,
> iov.iov_len);


So what does this do for performance? I'd expect that adding another
dive into the socket layer will come with penalties.


-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com