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Thread: Worksharing Monitor Low Virtual Memory is a hoax

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    All AUGI, all the time DoTheBIM's Avatar
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    Default Worksharing Monitor Low Virtual Memory is a hoax

    I just set up two users to work on the same file and installed the worksharing monitor. They are getting a warning about low virtual memory through the monitor (not through xp). Specs are xp 32bit 3GB ram. a message pops up saying available vm is 198mb and the desired vm is at 200mb. The paging file is in Gigabytes so this should not even be releavant at 200 megabytes. Should I be worried or is it a false alarm?

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    The warning is probably correct. You need 4 gig with the 3 gig switch set. Even with that, you will still get the VM warning if you have a lot of windows open or really intense windows or during a long Revit session. Revit has a memory leak so most recommend that you close over Revit +/- 4 hr sessions.

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    All AUGI, all the time DoTheBIM's Avatar
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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    We don't use 3GB switch. We have 3GB of RAM.

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    and the file is only 54.5 megs

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    File size x20 is the rule of thumb I've heard for the memory used by Revit alone for a single file. Factor in everything else going on over the course of the day and you can see why this can be a problem.

    I use Revit 2011 on my home machine with 2 GB RAM, and it works fine with smaller projects. But my current project file is up over 50 MB and my home machine simply can't take it. I have to work through remote desktop if I need to work on it at home, whereas otherwise I just use my VPN connection alone.

    So yeah, 55+ MB is most likely going to have problems with only 3GB system memory (minus +/- 1GB for system stuff, minus 1+ GB for the Revit file, and that leaves very little for anything else).

    I used to always have issues towards the end of the day in 2010 when I had XP x86 even with 4GB and the 3GB switch. PDF's wouldn't open, couldn't browse network locations, etc.
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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    Yes, you have three gigs, the Windows OS takes amost a gig. The Revit program can take another chunk of memory to load, then the Revit File expands off of disk by 4 or more times the file size, and the longer between STC, the bigger the file gets in memory, due to the undo iti s storing in memory, etc.

    All that said, a 54.5 gig file should in 2009 work great. In 2010, it'll work so-so, and in 2011, it may not, since the Revit Program gets larger each release.

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    Quote Originally Posted by Scott Womack View Post
    All that said, a 54.5 meg file should in 2009 work great. In 2010, it'll work so-so, and in 2011, it may not, since the Revit Program gets larger each release.
    This isn't encoraging. We've worked on 70+ meg files individually with out a hitch. in both 2009 and 2011. Our template is 50+ megs to start. I've had 3 projects of this size open in 2009 across 2 sessions of Revit. We haven't been on 2011 long enough to have explored those limits yet. I still don't follow the logic of 200M available vs. 3,096M allocated in xp virtual memory? Where's the other 2,896M at? And why is it not using the other 1Gb of Ram that windows says is available?
    Last edited by DoTheBIM; 2010-07-20 at 10:42 PM. Reason: fix megs vs. gigs

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    Might look at journal files to see what it reports for VM use. You should probably open a SR with Autodesk and tell them of the issue and your workstation specs, and send them journal files also from sessions where you see this warning, so they can analyze it.
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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    Quote Originally Posted by DoTheBIM View Post
    This isn't encoraging. We've worked on 70+ gig files individually with out a hitch. in both 2009 and 2011. Our template is 50+ gigs to start. I've had 3 projects of this size open in 2009 across 2 sessions of Revit. We haven't been on 2011 long enough to have explored those limits yet. I still don't follow the logic of 200M available vs. 3,096M allocated in xp virtual memory? Where's the other 2,896M at? And why is it not using the other 1Gb of Ram that windows says is available?
    Two things are going on here. First off, in 32 bit Windows, any given app only get's access to 2Gb of virtual address space. That virtual address space references both physical ram and virtual memory at the OS, but the application just thinks it has 2Gb of dedicated memory to play in. That is virtual memory in a nutshell. So any given app can crash if it tries to use more than 2Gb of address space, no matter how much memory is present as physical ram or swap file.
    The 3Gb switch makes 3Gb of address space available to applications, while only 1Gb is available to Windows itself. This is because 32 bit Windows can only handle 4Gb of total address space, and at any given moment it is dealing with the virtual address space for itself and a single app. Without the 3Gb switch it is 2/2, with the 3Gb switch it is a 3/1 split, and using the USERVA switch you can tweak it further, say 2.8/1.2. Because of how Windows maps graphics RAM, a large graphics card can make only 1Gb of address space for Windows a problem, thus the tweaking with USERVA to maximize address space for apps, while still allowing enough for Windows to function. Of course Revit is one of the very few apps still that needs more than 2Gb of address space. Exchange and SQL also can. And some audio and video editing apps probably.
    Anyway, no matter what, if an app tries to access more ram than the available address space allows, you crash. Maybe only half a gig of Revit is in RAM, and the rest is swap file, but if Revit needs to address 2.5 GB of address space, and you don't have the 3Gb switch applied, then you crash even if you have 4Gb of RAM and a 16Gb swap file. The resources are there but Revit can't access it.

    Also, the swap file is a shared resource, but as far as I can tell Worksharing Monitor only reports how much Revit is trying to use. So if Revit needs to use 200 Mb of virtual ram, and you have 2Gb allocated but only 150 Mb is available to Revit, again you crash. And being a shared resource, every open app, plus Windows, could be dipping into that 3Gb swap file you have allocated. I think a fragmented swap file can alos impact how well it gets allocated to apps, and if Windows is dynamically managing the swap file (default setting in XP) on a hard drive without much space and not recently defragged, you can have problems.
    In any case, the general rule in 32 bit Windows XP was to set the swap file to twice the physical ram, and make it a fixed size so it couldn't fragment. I have seen machines where this was set when the machine had 1Gb of RAM, and thus a fixed 2Gb swap file. A year later the machine had 3Gb of ram and still that 1Gb swap and was crashing, even with more RAM, because windows was trying to page to a very tiny swap file.

    The benefit of 64 bit Windows is that the address space goes to something like 2Tb, so there is no way you will crash from running out, even if Windows has half of that dedicated to itself, we are just FAR from Revit trying to access 1000 Gb of memory, as that would be a 50Gb file on disk! That alone means that 64 bit Windows can be more stable than 32 bit Windows on the same amount of RAM, even 2Gb. It may be slower because it has to page more, but it is more stable because it CAN page more. Add more RAM and it is stable and fast. Thus 64 bit Windows and 4Gb of RAM is to me a minimal machine these days, even for small residential work. Just no reason not to, and upgrades to 8Gb, 16Gb or more can be done as needed. But only if you have a 64 bit OS to start with.

    Oh, one other issue I have noticed. File size on disk is only part of the picture. How the app uses RAM also impacts things. In Revit 2010 and earlier, an export to DWG would not release memory used to make each DWG until the entire DWG export was complete. Basically a memory leak due to code logic. So a 10 Mb file could crash in 64 bit Windows with 32Gb of RAM and 64 Gb of swap file. Just ask it to export 1000 DWGs and watch the available resources drop till you crash. And yet the "x20" rule suggests that you have no memory problems at all!
    2011 releases the memory used to create each DWG as the DWG is written to the hard drive, so even a huge file that is using 90% of the available RAM could export 20,000 DWGs with no issues. But things like Audit and upgrade still don't release memory till the process completes, so you need some memory headroom to complete those tasks. Headroom being address space, physical ram and swap file in 32 bit windows, and only the latter two in 64 bit Windows. But still, run out of any of the three and you crash.


    Gordon

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    Default Re: Worksharing Monitor Low Virtual Memory is a hoax

    Wow Gordon, awesome post - even to me who knows more than the "average joe" about computers (and thus shoved into an "IT" position of sorts in my office )
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