Re: [Qemu-devel] [PATCH] slirp: disable Nagle in outgoing connections

[Kamil Rytarowski]

This patch is correct. LLDB expects 1sec for reply, GDB by default 2.

Debuggers use this option to disable Nagle algorithm in order to quickly
transfer messages between gdb-server and gdb-client. It's also fairy
portable across systems.

On 04.01.2018 18:56, Andreas Gustafsson wrote:
> slirp: disable Nagle in outgoing connections
> 
> When setting up an outgoing user mode networking TCP connection,
> disable the Nagle algorithm in the host-side connection.  Either the
> guest is already doing Nagle, in which case there is no point in doing
> it twice, or it has chosen to disable it, in which case we should
> respect that choice.
> 
> This change speeds up GDB remote debugging over TCP over user mode
> networking (with GDB runing on the guest) by multiple orders of
> magnitude, and has been part of the local patches applied by pkgsrc
> since 2012 with no reported ill effects.
> 
> Signed-off-by: Andreas Gustafsson <address@hidden>

Signed-off-by: Kamil Rytarowski <address@hidden>

> ---
>  slirp/tcp_subr.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
> index da0d53743f..8d0f94b75f 100644
> --- a/slirp/tcp_subr.c
> +++ b/slirp/tcp_subr.c
> @@ -416,6 +416,8 @@ int tcp_fconnect(struct socket *so, unsigned short af)
>      socket_set_fast_reuse(s);
>      opt = 1;
>      qemu_setsockopt(s, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(opt));
> +    opt = 1;
> +    qemu_setsockopt(s, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
>  
>      addr = so->fhost.ss;
>      DEBUG_CALL(" connect()ing")
>

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