netdev - Re: [PATCH] tcp: allow splice() to build full TSO packets

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Date:	Wed, 04 Apr 2012 02:20:06 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, ncardwell@...gle.com, therbert@...gle.com,
	ycheng@...gle.com, hkchu@...gle.com, maze@...gle.com,
	maheshb@...gle.com, ilpo.jarvinen@...sinki.fi, nanditad@...gle.com
Subject: Re: [PATCH] tcp: allow splice() to build full TSO packets

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 04 Apr 2012 08:15:28 +0200

> On Tue, 2012-04-03 at 18:50 -0400, David Miller wrote:
> 
>> Eric, sorry to be a pain, but to clear my conscience can you tell me
>> if the sendfile() path do the right thing with your change too?
>> 
>> I'm concerned about returning back into userspace without at least
>> one tcp_push() at the end.
> 
> Absolutely, this patch also handles the sendfile() path.
> 
> do_sendfile() ->
>  do_splice_direct() ->
>   splice_direct_to_actor() -> 
>    ...
>     splice_from_pipe() ->
>      splice_from_pipe_feed() ->
>       pipe_to_sendpage()  more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len
>        sock_sendpage() if (more) flags |= MSG_MORE;
>         kernel_sendpage()
>          inet_sendpage()
>           tcp_sendpage()
> 
> So the push is perfomed at the end (last page doesnt have MSG_MORE flag)

Perfect, thanks for double checking.
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