The KD protocol is fairly ?chatty?, and it?s completely serialized, with only one request-response in flight at a time. Operations like breaking into the debugger require many requests (e.g. read memory, read registers, ?), and this makes KD get painfully slow very quickly once you start adding any non-trivial latency in there. (You can see this by using kdsrv to project the kd protocol over a network, and then trying to use it on practically anything that?s not a LAN link.)
(This is also related to why closing memory/registers/disassembly windows will improve the responsiveness of KD, as that?s less talking to be done on every state change of the target.)
I seem to recall Bluetooth tending to add somewhere around 10ms or so latency (PAN, DUN over serial port), though those admittedly have more things layered on top of them (although DUN over serial should I think be pretty close to what you would be doing.) Could be crummy implementations too, but in general, it?s not pretty to use KD once you start adding a lot of transport latency into the mix between the target and the debugger.
(The WinDbg remote debugging protocols are much more tolerant of latency than the raw KD wire protocol.)
- S
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Jim Donelson
Sent: Monday, October 06, 2008 11:59 AM
To: Kernel Debugging Interest List
Subject: Re: Re:[windbg] Using serial-to-BT wireless
Interesting - sensitive in what way? We have not seen any noticeable difference.
Seems to work as good as a cable. Perhaps when the link is all on dedicated hardware (the pc is not involved in anyway) and with purpose driven engineering, they don’t have a significant delay. I would think a 10ms delay would generally spoil cable emulation in other applications as well.
On Mon, Oct 6, 2008 at 12:51 AM, Skywing > wrote:
Bluetooth adds non-trivial latency though, as I recall. The KD protocol is (highly) latency sensitive. Even adding 10ms makes things significantly more painful.
- S
From: xxxxx@lists.osr.commailto:xxxxx [mailto:xxxxx@lists.osr.commailto:xxxxx] On Behalf Of Jim Donelson
Sent: Monday, October 06, 2008 12:27 AM
To: Kernel Debugging Interest List
Subject: Re: Re:[windbg] Using serial-to-BT wireless
Doron,
115K baud is a 115K regardless of how you connect it.
If he is talking about the BlueTooth cable replacements then they look just like a real serial port on both ends.
We use them and they are just as good as long cable.
Do us all a real favor if you can. Get a KB out for XP that fixes the firewire driver to work with VIA chipsets and or add USB to XP.
For the for see able future, the “rest of us” still have to debug with XP, and unless you have the magic firewire chipset, most of use use 115K serial links.
Ya, I know - I’m dreaming.
Jim
On Sun, Oct 5, 2008 at 10:44 PM, Doron Holan > wrote:
Why would even want to run over bluetooth? The debug speed would be abysmal. The target side (i.e. the machine being debugged) needs to see a UART at the hardware level, not the software/emulation level.
d
-----Original Message-----
From: xxxxx@lists.osr.commailto:xxxxx [mailto:xxxxx@lists.osr.commailto:xxxxx] On Behalf Of Martin O’Brien
Sent: Thursday, June 26, 2008 3:52 PM
To: Kernel Debugging Interest List
Subject: Re:[windbg] Using serial-to-BT wireless
Interesting question; unfortunately, I don’t know the answer. It seems like it should work as the target side would presumably see
a UART, lack of which is usually the deal breaker for WinDbg transport alternatives. Where you lose me is the part about needing
one on the host side, because it seems like you would have to, as WinDbg can’t connect over Bluetooth, but I think that I’m missing
something.
Good luck,
mm
I?aki Castillo wrote:
> Has anyone used a serial-to-Bluetooth wireless device for the target
> machine ?
> I mean, something like this:
> http://www.sena.com/products/industrial_bluetooth/sd.php?domain=buysena_website
>
> If so, have you been able to connect using a simple Bluetooth board on
> the Windbg side, or is it necessary to have serial-to-BT boards on both
> sides ?
>
> Do you recommend any specific brand ?
>
> Inaki.
>
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