[sldev] UDP to TCP/HTTP - performance issues?

Kelly Linden kelly at lindenlab.com
Wed Nov 14 16:18:45 PST 2007


Callum Lerwick wrote:
> On Wed, 2007-11-14 at 23:57 +1100, Tateru Nino wrote:
>   
>> I'm noting a suspicious stall in the viewer when a presence popup
>> happens. Disabling the popup does not seem to change the behaviour.
>> Getting a friend to log in and log out, the viewer still stalls for a
>> second or so around the time the popup _would_ have appeared if it were
>> enabled. That's another data point for you.
>>     
>
> I've noticed this too. My wife has even complained about it. At one
> point it would even crash, though that seems to have been fixed.
>
> I've also noticed that during periods of high (total?) packet loss, the
> viewer will completely freeze. Which happens often when you're on a less
> than stellar wireless connection. No screen refreshes, CPU usage drops
> to zero. Why is network IO capable of blocking the graphics engine? The
> rest of the machine remains responsive, so I don't think its an
> X11/OpenGL problem.
>   
Even if you choose not to show the alerts the same data is sent to your
viewer.  When you log in that is a list of all your friends that are
online, when a friend logs in or out it is a single message with the ID
and online status.  This should be a really small packet of info, and I
think it is still UDP.  If there is a stall here I bet it has something
to do with however we are storing friends in memory - some bug that
makes inserting into that list really slow on large lists perhaps?  I
have not recently looked at this code so am guessing here, but that is
the first place I would look.

 - Kelly
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