Re: [Qemu-devel] [PATCH] Kick io-thread on qemu_chr_accept_input

[Anthony Liguori <aliguori@us.ibm.com>]

On 03/16/2012 07:25 AM, Jan Kiszka wrote:
> Once a chr frontend is able to receive input again, we need to inform
> the io-thread about this fact. Otherwise, main_loop_wait may continue to
> select without the related backend file descriptor in its set. This can
> cause high input latencies if only low-rate events arrive otherwise.
>
> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>

I'm not nacking this patch, but please note that this is a band-aid as not all 
char devices actually use qemu_chr_accept_input().

Regards,

Anthony Liguori

> ---
>
> /me wonders if a similar issue explains the slirp slowness under KVM
> with in-kernel irqchip enabled. Need to check...
>
>   qemu-char.c |    1 +
>   1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/qemu-char.c b/qemu-char.c
> index 9a5be75..a589a84 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -177,6 +177,7 @@ void qemu_chr_accept_input(CharDriverState *s)
>   {
>       if (s->chr_accept_input)
>           s->chr_accept_input(s);
> +    qemu_notify_event();
>   }
>
>   void qemu_chr_fe_printf(CharDriverState *s, const char *fmt, ...)