Btw, here is a little demo of the 16 * 720p wall driven by virtualbox https://www.youtube.com/watch?v=eFAATNofjHA&feature=youtu.be
2014-08-28 23:03 GMT+03:00 Rūdolfs Bundulis <[email protected]>: > Hi Klaus, > > > Was the available monitor hardware limiting you to 16? Because with 720p > and the XPDM driver (which is usable with Win7, and I think still the > default if you don't enable 3D in the guest additions installer) you should > be able to run > with 5x5, too. Needs "only" 226MB for the framebuffers. > > Well, that is the thing, I don't have the 3D checkbox checked, guest > Windows does not allow to enable Aero (so I can assume WDDM is not used?) > but the memory bar still warns me when I go above 8 monitors (seems that it > always calculates 3 surfaces. Is there any way to check if XPDM or WDDM is > actually being used? I could then confirm and fallback to XPDM if that > gives me more screens. What I saw in practice is that 7 monitors booted > fine in Full HD, when I ran 8 my hint to use 1920x1080 was ignored and all > 8 monitors got 1600x1200 resolution, increasing above 10 pushes the > resolution down to 1400 x 1050 and so on until when booting with 25 Windows > reports only one display at 800x600 (I guess it is simply an overkill for > the VRAM). If I could verify if WDDM/XPDM is being used it would become > more clear if I can go higher. > > > Another option might be using 15 or 16bpp in the guest *and* on the host > (otherwise color format conversion is necessary, and this kills performance > as VirtualBox uses the CPU for that). The GUI again is pessimistic and > always ? > expects 24bpp (4 bytes, the packed format again is unbearably > slow as it needs conversion), but the virtualizer would work just fine. > This would fit into 248MB with 5x5 @1920x1080. Yes, the reduced color > resolution sucks, it usually results in heavy color banding. > > One of the guys involved on our side also suggested this, but we are > perofming live video encoding from the framebuffer, 32bpp is great since > that can be fed directly to the encoder, anything else will have to be > repacked which would not be feasable. Not sure, but since Xubuntu ran > really slow, I have a theory that the offscreen surfaces could actually be > very useful, since if X11 syncs every draw with the primary surface and > locks it, and my software also needs to lock the surface for to at least > copy the data, this could be the reason why Xubuntu performs poorly. > > > Oh sure, we know that VirtualBox can do amazing things (in some areas > going far beyond what any virtualizer out there can do), and often shows > its great scalability in setups which are a little outside the norm :) > > Yeah, I am really impressed, when I started my PhD work I was a lot in the > dark, wanted to write virtual video card drivers etc., but this is flexible > scalable and great, of course if the VRAM limit can be broken. Well I'll > lurk around the sources and try to get a grasp of the VRAM things, maybe it > is possible to do something there. Thanks a lot for all the input. > > > 2014-08-28 22:12 GMT+03:00 Klaus Espenlaub <[email protected]>: > > Rūdolfs, >> >> >> On 28.08.2014 18:15, Rūdolfs Bundulis wrote: >> >>> Hi Klaus, >>> >>> I'll mail directly to you this time, since this is not regarding the >>> original issue. >>> >> >> Actually if you'd stay on the list then you'd have a chance of getting >> more than one team member's knowledge... I'm not really a graphics expert. >> >> >> I ran some tests today, and it seems that at least on >>> Windows 7 16 monitors on 1280x720 (720p) work fine. Using our software I >>> streamed that to a 4x4 22" monitor wall and that looked really >>> impressive. >>> >> >> Was the available monitor hardware limiting you to 16? Because with 720p >> and the XPDM driver (which is usable with Win7, and I think still the >> default if you don't enable 3D in the guest additions installer) you should >> be able to run with 5x5, too. Needs "only" 226MB for the framebuffers. >> >> Another option might be using 15 or 16bpp in the guest *and* on the host >> (otherwise color format conversion is necessary, and this kills performance >> as VirtualBox uses the CPU for that). The GUI again is pessimistic and >> always expects 24bpp (4 bytes, the packed format again is unbearably slow >> as it needs conversion), but the virtualizer would work just fine. This >> would fit into 248MB with 5x5 @1920x1080. Yes, the reduced color resolution >> sucks, it usually results in heavy color banding. >> >> >> Also tried Xubuntu 14.04 on same configuration but for >>> somewhat reason (X11) it was lagging terribly. The question that arose >>> was, could you at least provide some base info (as far as it does not >>> take too much of your time) what needs to be patched to increase the >>> VRAM size? >>> >> >> The easy part is VGA_VRAM_MAX in src/VBox/Devices/Graphics/DevVGA.h and >> VRAMSize in src/VBox/Main/xml/VirtualBox-settings.xsd. Not sure if there >> are a few more "256 MB" definitions somewhere. >> >> I bet you'll run into trouble with PCI resource allocation (in our case >> done in the code before the VM starts, not in the BIOS like with >> conventional PCs), because the bigger area will not fit into the PCI hole >> (which is actually normal, I think real systems start with a partial >> mapping of the VRAM there, and the graphics driver then relocates it to a >> free area past 4GB, at least with 64 bit OSes which can deal properly with >> the then necessary 64 bit PCI resources). >> >> Similarly I guess the BIOS e820 memory map will most likely be broken. >> >> Many real graphics cards can work with a partially mapped VRAM, giving >> access only to 256MB at a time. This would need big changes to our virtual >> graphics card and the guest additions driver, but would minimize the need >> to change other places. >> >> >> Our research time consists of quite skilled developers so if >>> it is not a man-year we would be interrested at least to look into it, >>> since the 16@720p demo was impressive and seems that this technology has >>> a future, and currently the biggest limitation is the vram limit in >>> VirtualBox. Hope I'm not too intrusive, simply we were all quite >>> astonished how this leverages the independence from actual hardware in >>> display wall construction, so we are all keen to achieve at least a >>> 16x1080p implementation. >>> >> >> Oh sure, we know that VirtualBox can do amazing things (in some areas >> going far beyond what any virtualizer out there can do), and often shows >> its great scalability in setups which are a little outside the norm :) >> >> We added support for 64 screens in the days when no one could afford a >> full HD screen, and actually the majority of users had only 1024x768, and >> users were willing to use 16bpp... it blew the mind of quite a few users >> that they could hook up a collection of RDP clients, each providing a >> couple of monitors, and get a big video wall this way. >> >> Regards, >> Klaus >> >> >> >>> Best Regards, >>> Rudolfs Bundulis >>> >>> >>> 2014-08-27 20:11 GMT+03:00 Klaus Espenlaub <[email protected] >>> <mailto:[email protected]>>: >>> >>> >>> On 27.08.2014 <tel:27.08.2014> 18:38, Rūdolfs Bundulis wrote: >>> > Hi Klaus, >>> > >>> > Thanks again for the fast response. Well, this is a university >>> research >>> > project to build monitor walls without the underlying hardware, >>> so I >>> > guess its reasonable that I am breaking some limits that should be >>> > normal in a normal use case. >>> >>> As long as you're only going for high monitor counts, that's nothing >>> unexpected. >>> >>> > Regarding 3D, when I installed guest additions I checked the >>> Direct3D >>> > box but I dont have the "Enable 3D acceleration" checkbox checked >>> in >>> > the VirtualBox manager. Should I reinstall the guest additions >>> without >>> > Direct3D? >>> >>> Strange... I wonder why the GUI is so eager with insanely high VRAM >>> proposals. It should only care about the checkbox, because if that's >>> not >>> set then there is no 3D, period. >>> >>> From what I remember, the "rule of thumb" for the absolute minimum >>> VRAM >>> size (in bytes) is (x*y*4+4096+1048576)*count. At least it was >>> accurate >>> with the X11 driver, and the GUI seems to agree. It seems the XPDM >>> driver needs twice that much (because Windows needs one offscreen >>> surface), and with the WDDM driver it needs thrice that much (two >>> offscreen surfaces). >>> >>> Which guest OS are you using? Which driver did you install (for those >>> OSes which allow selecting)? >>> >>> > And more important, is it actually possible to fit 25 full hd >>> > (1920x1080) framebuffers in the video ram if it is only 256mb >>> inside >>> > virtualbox? I could try to recompile from sources with lets say >>> 1GB if >>> > redefining the video memory macro does not break other stuff. >>> >>> Barely... the above formula gives 223MB already, and if the Windows >>> driver really need the mentioned amount of offscreen memory you'd run >>> out of VRAM. I'd use VBoxHeadless to try this out actually, because >>> it >>> doesn't have any of those annoying safeguards to protect users from >>> shooting themselves in the foot. >>> >>> Increasing the VRAM size by recompiling will cause trouble, as it >>> would >>> need drastic changes to the memory layout (PCI memory hole, ...), and >>> I'm quite sure that we looked at it and considered it too much >>> effort. >>> Everything is doable in the end, that's the good and bad thing about >>> software :) >>> >>> Klaus >>> >>> > Best Regards, >>> > Rudolfs Bundulis >>> > From: Klaus Espenlaub >>> > Sent: 2014.08.27 <tel:2014.08.27>. 19:05 >>> > To: [email protected] <mailto:[email protected]> >>> >>> > Subject: Re: [vbox-dev] Monitor count limitations >>> > Hi Rūdolfs, >>> > >>> > On 27.08.2014 <tel:27.08.2014> 16:49, Rūdolfs Bundulis wrote: >>> >> Hi, >>> >> >>> >> I've run into some more issues with high monitor count on >>> VirtualBox. >>> >> Basically when selecting 25 displays it complains that at least >>> 600 >>> >> something MB of VRAM is needed, but while the arrows in the >>> display >>> >> number box allow to select more than 8 monitors, seems that i >>> can't go >>> >> above 256 mb in VRAM. Is this a hard limitation? Since the COM >>> API also >>> >> does not allow me to set more than that. >>> > >>> > Sounds like you have 3D enabled - then the GUI does a little too >>> simple >>> > maths, extrapolating the necessary space beyond sanity. It's only >>> a >>> > proposal, not a hard "must have". Don't think anyone tried to go >>> to such >>> > extremes, because it's just nonsense to expect even basic 3D able >>> to >>> > cope with so many screens. >>> > >>> > If you disable 3D then the requirements should be a lot lower, in >>> the >>> > order of what's needed to represent the pixels. >>> > >>> > Yes, there is currently a hard limit of 256 MiB VRAM, and we >>> didn't find >>> > cases where it was absolutely necessary to have more. >>> > >>> > Klaus >>> >> Best Regards, >>> >> Rudolfs Bundulis >>> >> >>> >> >>> >> 2014-06-18 13:41 GMT+03:00 Rūdolfs Bundulis >>> <[email protected] <mailto:[email protected]> >>> >> <mailto:[email protected] >>> >>> <mailto:[email protected]>>>: >>> >> >>> >> Hi Klaus, >>> >> >>> >> Thanks a lot for the clarification. I thought the same that >>> it was >>> >> just a sanity limit, but in my case this is really needed. >>> Then I >>> >> guess will be able to do the same with the COM API, thanks >>> a lot again. >>> >> >>> >> >>> >> 2014-06-18 13:13 GMT+03:00 Klaus Espenlaub >>> >> <[email protected] >>> <mailto:[email protected]> >>> <mailto:[email protected] >>> >>> <mailto:[email protected]>>>: >>> >> >>> >> Hi Rūdolfs, >>> >> >>> >> On 18.06.2014 11:48, Rūdolfs Bundulis wrote: >>> >> > Hi, >>> >> > >>> >> > I'm developing a system that needs to run a headless >>> VM with >>> >> a large >>> >> > number of attached monitors - currently the GUI has >>> the limit >>> >> to set >>> >> > maximum monitor count to 8, I didn't check the COM >>> API myself >>> >> but I >>> >> > suspect that it will not allow me to set the count >>> greater >>> >> than 8, while >>> >> > browsing the VirtualBox sources show that the >>> internal C macro is >>> >> > defined to 64: >>> >> > >>> >> > /* this should be in sync with monitorCount >>> <xsd:maxInclusive >>> >> > value="8"/> in >>> >> src/VBox/Main/xml/VirtualBox-settings-common.xsd */ >>> >> > #define VBOX_VIDEO_MAX_SCREENS 64 >>> >> >>> >> Looks to me that this comment is simply outdated. >>> Nothing more, >>> >> nothing >>> >> less. >>> >> >>> >> Many limits can be listed with "VBoxManage list >>> >> systemproperties", and >>> >> it shows 64. >>> >> >>> >> > Is there really a need to limit the count to 8? If I >>> change >>> >> the xml >>> >> > schema file and increase the count from 8 to 64 and >>> recompile >>> >> would >>> >> > there be any actual limitations in the VirtualBox >>> core? >>> >> >>> >> There is a constant conflict in the GUI between sanity >>> (i.e. >>> >> protecting >>> >> users against their stupidity - you can't believe how >>> many people >>> >> believe that more is better, even if it's a giant waste >>> of resources >>> >> instead) and allowing expert users to go to the >>> extreme. There are >>> >> extremely few people out there who ever need to deal >>> with more >>> >> than 8 >>> >> monitors. >>> >> >>> >> In my quick test I could use the GUI to select 20 >>> monitors - >>> >> sure, the >>> >> slider doesn't allow that, but one can enter the number >>> or use the >>> >> up/down arrows. This needs 256MB of VRAM, which this >>> high number >>> >> automatically unlocks. >>> >> >>> >> Klaus >>> >> >>> > >>> >>> >
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