linux-kernel - Re: [PATCH] tcp: splice as many packets as possible at once

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Message-Id: <20090113.160505.178961721.davem@davemloft.net>
Date:	Tue, 13 Jan 2009 16:05:05 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	w@....eu, ben@...s.com, jarkao2@...il.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	jens.axboe@...cle.com
Subject: Re: [PATCH] tcp: splice as many packets as possible at once

From: Eric Dumazet <dada1@...mosbay.com>
Date: Sat, 10 Jan 2009 00:34:40 +0100

> David, do you think we still must call __tcp_splice_read() only once
> in tcp_splice_read() if SPLICE_F_NONBLOCK is set ?

You seem to be working that out in another thread :-)

> [PATCH] tcp: splice as many packets as possible at once
> 
> As spotted by Willy Tarreau, current splice() from tcp socket to pipe is not
> optimal. It processes at most one segment per call.
> This results in low performance and very high overhead due to syscall rate
> when splicing from interfaces which do not support LRO.
> 
> Willy provided a patch inside tcp_splice_read(), but a better fix
> is to let tcp_read_sock() process as many segments as possible, so
> that tcp_rcv_space_adjust() and tcp_cleanup_rbuf() are called less
> often.
> 
> With this change, splice() behaves like tcp_recvmsg(), being able
> to consume many skbs in one system call. With typical 1460 bytes
> of payload per frame, that means splice(SPLICE_F_NONBLOCK) can return
> 16*1460 = 23360 bytes.
> 
> Signed-off-by: Willy Tarreau <w@....eu>
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

I've applied this, thanks!
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