netdev - Re: [RFC PATCH] tcp: Add SOF_TIMESTAMPING_TX_EOR and allow MSG_EOR in tcp

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Date:	Mon, 28 Mar 2016 21:31:03 -0700
From:	Yuchung Cheng <ycheng@...gle.com>
To:	Martin KaFai Lau <kafai@...com>
Cc:	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Network Development <netdev@...r.kernel.org>,
	Kernel Team <kernel-team@...com>,
	Eric Dumazet <edumazet@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [RFC PATCH] tcp: Add SOF_TIMESTAMPING_TX_EOR and allow MSG_EOR in tcp_sendmsg

On Sun, Mar 27, 2016 at 10:42 PM, Martin KaFai Lau <kafai@...com> wrote:
>
> On Fri, Mar 25, 2016 at 04:05:51PM -0700, Yuchung Cheng wrote:
> > Looks like an interesting and useful patch. Since HTTP2 allows
> > multiplexing data stream frames from multiple logical streams on a
> > single socket,
> > how would you instrument to measure the latency of each stream? e.g.,
> >
> > sendmsg of data_frame_1_of_stream_a
> > sendmsg of data_frame_1_of_stream_b
> > sendmsg of data_frame_2_of_stream_a
> > sendmsg of data_frame_1_of_stream_c
> > sendmsg of data_frame_2_of_stream_b
>
> A quick recall from the end of the commit message:
> "One of our use case is at the webserver.  The webserver tracks
> the HTTP2 response latency by measuring when the webserver
> sends the first byte to the socket till the TCP ACK of the last byte
> is received."
>
> It is the server side perception on how long does it take to deliver
> the whole response/stream to the client.  Hence, the number of
> interleaved streams does not matter.
>
> Some sample use cases are,
> comparing TCP sysctl/code changes,
> observing encoding/compression impact (e.g. HPACK in HTTP2).
>
> Assuming frame_2 is the end stream for 'a' and 'b':
> sendmsg of data_frame_1_of_stream_a
> sendmsg of data_frame_1_of_stream_b
> sendmsg of data_frame_2_of_stream_a MSG_EOR
> sendmsg of data_frame_1_of_stream_c
> sendmsg of data_frame_2_of_stream_b MSG_EOR
>
> Are you suggesting other useful ways/metrics should be measured in
> this case?
No this is what I have in mind but wanted to confirm. Thanks.