[Qemu-devel] [PATCH v2] vnc: Set default kbd delay to 10ms

[Qemu-devel] [PATCH v2] vnc: Set default kbd delay to 10ms

[Alexander Graf]

The current VNC default keyboard delay is 1ms. With that we're constantly
typing faster than the guest receives keyboard events from an XHCI attached
USB HID device.

The default keyboard delay time in the input layer however is 10ms. I don't know
how that number came to be, but empirical tests on some OpenQA driven ARM
systems show that 10ms really is a reasonable default number for the delay.

This patch moves the VNC delay also to 10ms. That way our default is much
safer (good!) and also consistent with the input layer default (also good!).

Signed-off-by: Alexander Graf <agraf@suse.de>

---

v1 -> v2:

  - Clarify commit message
---
 qemu-options.hx | 2 +-
 ui/vnc.c        | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 76b1c67..6909285 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1753,7 +1753,7 @@ spec but is traditional QEMU behavior.
 @item key-delay-ms
 
 Set keyboard delay, for key down and key up events, in milliseconds.
-Default is 1.  Keyboards are low-bandwidth devices, so this slowdown
+Default is 10.  Keyboards are low-bandwidth devices, so this slowdown
 can help the device and guest to keep up and not lose events in case
 events are arriving in bulk.  Possible causes for the latter are flaky
 network connections, or scripts for automated testing.
diff --git a/ui/vnc.c b/ui/vnc.c
index 26136f5..eb91559 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -3808,7 +3808,7 @@ void vnc_display_open(const char *id, Error **errp)
     }
 
     lock_key_sync = qemu_opt_get_bool(opts, "lock-key-sync", true);
-    key_delay_ms = qemu_opt_get_number(opts, "key-delay-ms", 1);
+    key_delay_ms = qemu_opt_get_number(opts, "key-delay-ms", 10);
     sasl = qemu_opt_get_bool(opts, "sasl", false);
 #ifndef CONFIG_VNC_SASL
     if (sasl) {
-- 
1.8.5.6

Re: [Qemu-devel] [PATCH v2] vnc: Set default kbd delay to 10ms

[Daniel P. Berrange]

On Wed, Jul 12, 2017 at 02:43:45PM +0200, Alexander Graf wrote:
> The current VNC default keyboard delay is 1ms. With that we're constantly
> typing faster than the guest receives keyboard events from an XHCI attached
> USB HID device.
> 
> The default keyboard delay time in the input layer however is 10ms. I don't know
> how that number came to be, but empirical tests on some OpenQA driven ARM
> systems show that 10ms really is a reasonable default number for the delay.
> 
> This patch moves the VNC delay also to 10ms. That way our default is much
> safer (good!) and also consistent with the input layer default (also good!).

And that still allows 100 keys to be sent in 1 second. If people are needing
to send more than this, they should be using a paravirt channel like the
SPICE agent which support high volume text cut + paste to the guest OS.

> 
> Signed-off-by: Alexander Graf <agraf@suse.de>

Reviewed-by: Daniel P. Berrange <berrange@redhat.com>


> ---
>  qemu-options.hx | 2 +-
>  ui/vnc.c        | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 76b1c67..6909285 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1753,7 +1753,7 @@ spec but is traditional QEMU behavior.
>  @item key-delay-ms
>  
>  Set keyboard delay, for key down and key up events, in milliseconds.
> -Default is 1.  Keyboards are low-bandwidth devices, so this slowdown
> +Default is 10.  Keyboards are low-bandwidth devices, so this slowdown
>  can help the device and guest to keep up and not lose events in case
>  events are arriving in bulk.  Possible causes for the latter are flaky
>  network connections, or scripts for automated testing.
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 26136f5..eb91559 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -3808,7 +3808,7 @@ void vnc_display_open(const char *id, Error **errp)
>      }
>  
>      lock_key_sync = qemu_opt_get_bool(opts, "lock-key-sync", true);
> -    key_delay_ms = qemu_opt_get_number(opts, "key-delay-ms", 1);
> +    key_delay_ms = qemu_opt_get_number(opts, "key-delay-ms", 10);
>      sasl = qemu_opt_get_bool(opts, "sasl", false);
>  #ifndef CONFIG_VNC_SASL
>      if (sasl) {
> -- 
> 1.8.5.6
> 
> 

Regards,
Daniel
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