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

David Miller
2009-01-14T00:05:22Z

From: Eric Dumazet <dada1@cosmosbay.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@1wt.eu>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

I've applied this, thanks!