Request: RealVNC no display mode

[James Weatherall]

Feico,

Understood.  The version you are using includes one optimisation for
Win2VNC-like clients, which is why the resource consumption appears to be
around half of when a normal viewer is connection.

Your assessment of the cause of the resource consumption is correct - VNC
Server must keep both a buffer to blit the physical display into, and a
comparison buffer.  The comparison buffer is optimised to only exist if at
least one update request has been received since there were last no clients
connected.

Your assessment of accounting for when to release the blit buffer is
incorrect - but hey, 1 out of 2 isn't bad! :)  Accounting for release of the
buffer is actually simpler than that and the hard bit is actually handling
"lazy" allocation of the blit buffer in the first place.

That level of optimisation hasn't been a priority for us because
Win2VNC/x2vnc etc are relatively obscure tools & because desktop systems
tend to have huge amounts of memory at their disposal.  (A typical XP system
seems to take about 140Mb just for a single user logged on with no other
programs running, for example!).  If a simple & safe solution becomes
apparent then we'll certainly consider including it.

Cheers,

Wez @ RealVNC Ltd.


> -----Original Message-----
> From: Feico de Boer (ML) [mailto:fdboer-ml "at" gmx.net] 
> Sent: 30 September 2004 14:53
> To: James Weatherall
> Cc: 'VNC-list'
> Subject: Re: Request: RealVNC no display mode
> 
> James Weatherall wrote:
> 
> > Which version of VNC Server are you using?  
> 
> I'm using version 4.00.0000.0026 as it reports itself. It is 
> the version that was send by you with the Win2VNC logon fix 
> if you remember.
> 
> In idle mode procexp (Sysinternals.com utility) reports a 
> memory consumption of 1 MB, connecting to the instance memory 
> jumps up to 10 MB. Of that an approximate 7 MB can be 
> accounted for by looking at the desktop size (2304x1024x24 = 7 MB).
> 
>  > VNC 4 already includes some code
> > to reduce resource consumption in the case where no updates 
> are ever 
> > requested, but further optimisation is possible.
> 
> True, if I connect to the server with the vncviewer, memory 
> usage jumps up to 20 MB. Still, 10 MB seems to me a pretty 
> big overhead for a few new class instances.
> 
> It looks to me (from the outside, don't know about the code) 
> that there is a global buffer allocated to bitblit the screen 
> into. Then if updates are requested, a second buffer is 
> allocated to determine the differences.
> 
> What (IMHO) should happend is that the first buffer should 
> only be allocated after the first update request saving the 
> memory in case no requests are made. However, if you had 
> multiple connections, it gets a bit harder to determine the 
> release of that first buffer. Keeping a update request 
> counter/flag per connection can help you there to determine 
> the neccessity of the buffer. (Just my 2 cents, might be 
> completely wrong here. ;-)
> 
> > We have plans to release a hooking driver as an optional add-on for 
> > VNC Server.
> 
> That would be great.
> 
> Regards,
> Feico.
> 
> >>-----Original Message-----
> >>From: vnc-list-admin "at" realvnc.com
> >>[mailto:vnc-list-admin "at" realvnc.com] On Behalf Of Feico de Boer (ML)
> >>Sent: 30 September 2004 13:34
> >>To: VNC-list
> >>Subject: Request: RealVNC no display mode
> >>
> >>Hello folks,
> >>
> >>I'm exploring the possibility of a 'no display mode' 
> >>connection option and would like to ask input from the 
> developers on 
> >>this.
> >>
> >>The reason for all of this. I use Win2VNC extensively to control my 
> >>laptop, Win2VNC acts as a remote keyboard/mouse using the 
> VNC server 
> >>as an extension cord. Occasionally I want also to use the remote 
> >>display functionality. I don't want to have different 
> services running 
> >>for this as it only takes up resources.
> >>
> >>However, due to my 2304x1024x24 desktop the VNC server eats 
> 10 MB that 
> >>I think is used as screenbuffer. As I'm short on memory in 
> general I 
> >>really could use that extra ten meg.
> >>
> >>Apart from this, any plans to implement mirror display drivers (or 
> >>just usage of it) for Windows in the (near) future?
> >>
> >>Regards,
> >>Feico.
> >>_______________________________________________
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