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    Revit Performance Drop Off

    So I have set out trying to figure out why at times when I am working Revit seems to just slow way down. After some google searching I came across an atricle stating that when the VM Size is bigger then the Mem Usage you will get the preformance drop.

    See attached Image.

    I have confirmed this to a tee. I will be work and for some reason Revit will drop almost all of its Mem and be working off the VM... Exactly at the same time I will notice that my project becomes very sluggish.

    Any idea on how to fix this problem? I have my page file turned off but I dont think you can stop VM. Is there a way to stop revit from dropping its Mem?
    Attached Files
    -Alex Cunningham

    #2
    Hi Alex,

    Please provide your hardware configuration - particularly the amount of RAM and the version of Windows (and whether it's 32 bit or 64 bit), but CPU and graphics card might be helpful as well.

    Also, provide a screen-shot of the Windows Task Manager showing the "Performance" tab.

    You should not have the Page File turned off. It should be set so that Windows automatically sets and adjusts it.

    Comment


      #3
      Alex,
      The Mem Usage number is how much RAM Revit is using. The Virtual Memory number (VM Size) is how much MEMORY Revit needs. The difference is on the hard drive, one way or the other. And when Revit is less than half present in RAM, you get a ton of thrashing of the hard drive and a major slowdown. You could check this by turning on the Page Faults column. If Revit has a lot of them happening as you watch you know Revit is thrashing.
      To make matters worse, you don't have a dedicated page file, so Windows is creating one on the fly to avoid Revit simply crashing. That just makes the paging even slower because likely there isn't contiguous space for a swap file and you are dealing with fragments all over the drive.
      So yeah, when VM size is a lot bigger than Mem Usage you will see problems. But the answer isn't to delete your page file, it is to get more RAM. Or figure out what is eating up so much of it, if this is occurring on the 6 GB machine that you posted benchmarks of. I suspect some other application has eaten up a lot of your available RAM, and forced Revit into paging. Or perhaps there is a memory leak somewhere? Does this happen (both the numbers in Task Manager & the performance hit) right after a fresh boot up, or only when the machine has been running for a while?
      Definitely some troubleshooting process to go thru.

      You may want to take a look at this site for some info.

      Gordon
      Pragmatic Praxis

      Comment


        #4
        I have turned on more of the columns in my task manager and will continue to monitor while working. I will post a updated ss after it does its mem dump again. Stay tuned


        I am running a HP Z400 workstation.
        XP Pro x64 SP2
        W3520 Xeon @ 2.67GHz
        7.98GB of ECC DDR3 @ 1333MHz
        Segate ST3250620AS
        Nvidia Quadro FX 1800 768MB
        Driver: 6.17.11.9703

        The projects I work in are at a max of 60MB and structural projects, but sometimes I do open both RAC and RST at the same time. I have never used more then 5GB of my commit charge. (I will post a SS of my preformacne tab later) I may be wrong but the nessicity of a page file only applies when you dont have error checking ram. I only recently disabled my pagefile, anyways doing so has increased my preformance. I have also started scheduled taskes to defrag and clean up my hard drive once a week.
        -Alex Cunningham

        Comment


          #5
          Originally posted by Alex Cunningham View Post
          I may be wrong but the nessicity of a page file only applies when you dont have error checking ram. I only recently disabled my pagefile, anyways doing so has increased my preformance.
          I can assure you that the page file has nothing to do with "error checking RAM". Windows eventually becomes unhappy when there is no page file, no matter how much RAM you have. Turning it off would not account for a general increase in performance.

          Generally speaking the VM column in the WTM in your SS is not the same as page swapping data because there's not enough physical RAM. That VM column is not what one would think it means - it doesn't (necessarily) have anything to do with the pagefile. It's the amount of memory being used by the process (but from what I understand, doesn't necessarily include everything, which is why it's often smaller than indicated by the "Mem Usage" column). The way Windows memory management works is that *all* memory is mapped through virtual address space.

          What this means is that there does appear to be something odd going on - Revit should be releasing the VM (i.e. virtual address space) more readily (it should be more in line with Mem Usage)... but I really don't think this has anything to do with your pagefile (though as I said before, it should be ON - let Windows manage its size automatically).

          Keep in mind that any "issues" with the VM/page file are a "symptom", not a "cause".

          If you simply close down Revit and reopen your project when this happens, does that fix things? Does it happen with every project? Any patterns?

          Comment


            #6
            Ok ill turn my PF back on. I havnt had a preformance issue since i turned it off though. I will see if it comes back.

            Closing Revit and waiting till the procees clears fixes the problem untill Revit dumps again. I can pinpoint any patterns as of yet. Not one project does it more. Every project does it and sometimes even when I am just making a simple family and thats the only thing open.
            -Alex Cunningham

            Comment


              #7
              Funny how things work sometimes. We have a user who is doing some REALLY intensive wall editing, and having a huge performance slowdown over time. She starts with about 3 GB of 8 GB in use, and over time her Modified RAM creeps up, from the less than 100 MB that is "normal" when you really aren't doing anything, to 3-4 GB, at which point there is no more "Free" RAM, and little "Standby", and hard faults are way high.

              I found this reference to a similar problem, with another Autodesk product. Now normally I wouldn't think that Inventor and Revit had much in common, but in 2011 Revit got a graphics engine update, as (I think) all Autodesk products now share a single graphics engine internally. Part of why some cool things like Ambient Occlusion and Ghosted Surfaces are now possible. Anyway, the link talks about switching Windows 7 swap file from Windows Managed to fixed matching Min and Max values. Which the person claims induces Windows to manage Modified RAM better. Interesting thought, and certainly wouldn't surprise me to find that Revit and Inventor might have interactions with underlying Windows systems that the other 99.99999% of Windows users would never see, and Microsoft might never bother to address as a result.
              In any case, I may switch this user to a fixed swap file and see what happens.

              Gordon
              Pragmatic Praxis

              Comment


                #8
                Originally posted by Gordon Price View Post
                Anyway, the link talks about switching Windows 7 swap file from Windows Managed to fixed matching Min and Max values. Which the person claims induces Windows to manage Modified RAM better. Interesting thought, and certainly wouldn't surprise me to find that Revit and Inventor might have interactions with underlying Windows systems that the other 99.99999% of Windows users would never see, and Microsoft might never bother to address as a result.
                In any case, I may switch this user to a fixed swap file and see what happens.
                I don't think so. it's possible Revit might have a memory leak that can be mitigated by throwing gobs of pagefile at it, but I think the symptoms would be more obvious if that were the case. I don't think that Revit and Inventor have any interaction with "underlying Windows systems" as in the pagefile... that's all handled by Windows memory management.

                Windows will typically set the "system managed" pagefile to the same amount as RAM. So with 8 GB of RAM, you should also have 8 GB of VM pagefile for a total of 16 GB of "memory". Windows will not attempt to adjust that 8GB of pagefile unless you run out of 16 GB of memory... and you will know long before that happens because your entire computer (not just Revit) will have ground to a halt.

                Comment


                  #9
                  I am just hoping there is some goofiness where Windows isn't very expeditious about writing Modified pages to disk with a Windows managed PF, but somehow a static PF makes Windows write those pages sooner. Grasping at straws, I know, but funny that another Autodesk product is seeing a similar performance hit with weird memory management behavior. The interaction I imagine is that most people don't have apps that are going to hammer on RAM and create the volume of Modified Pages that Revit does. Or Inventor. So while not a direct interaction, there is potentially a relationship. I hope.
                  For what it is worth, another member of the same team, with the same file open, is seeing maybe 55 MB of Modified RAM, while the user seeing the problem sees this climb steadily over the course of an hour or two until a good 3 GB or more is stuck in a Modified state, leaving no Free RAM so Revit is forced to Page. Nothing short of shutting down Revit free it. She is specifically doing a lot of Paint work, with a ton of colors on screen. We shall see.

                  Gordon
                  Pragmatic Praxis

                  Comment


                    #10
                    OK, I have no rational explanation. But...
                    My one user was consistently seeing Modified pages climb over the course of as little as an hour. Eventually there was no Free RAM at all and Revit had to start paging. Her Page File was configured for Windows to manage, and was set at 12240 minimum by Windows. I set it to a 12288 (exactly 1.5 times her 8 GB of RAM) min and max.
                    In 2 hours of work yesterday afternoon, and another three this morning, her Modified pages haven't moved much beyond 50 MB or so. This is not how memory management is supposed to work, nor is it how Microsoft claims it works. But sadly it seems like maybe it is the way it does work.

                    Alex, it would be interesting to see if XP x64 behaves similarly. I THINK the key is that the page file is a static size, but maybe start with the same 1.5X multiplier and see what happens?

                    Gordon
                    Pragmatic Praxis

                    Comment

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