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Thread: VERY odd Brush Lag Performance Issue

  1. #1
    Join Date
    Apr 2012
    Posts
    521

    VERY odd Brush Lag Performance Issue

    Description of How to Replicate the Issue :

    Using the custom Brush (note dab spacing is 5%)
    Mouse OR Stylus (it happens for either one)


    1. Using a relatively normal size 60% brush, make a singular large circular stroke and make it faster and faster... observe how fast one loop of the stroke can be without any lag.. i.e. get a feel for the fastest stable stroke speed.

    2. At some slightly higher stroke speed the drawn stroke will fall behind the brush position, BUT the drawn stroke will proceed at a much slower speed than the fastest stable stroke speed.. it will lag severely and will continue to do so until you let it catch up to your brush. If you do not let it catch up, the stroke precision eventually degrades. I understand how at one point the stroke would fall behind... and for the stroke to slow down because it is trying to save/cache brush positions of the stroke as well as draw.

    I am using the 64-bit version of ArtRage (Windows 7 pro) and 24Gigs RAM.


    Using resource monitor (Windows 7) it can be observed that during 1 above all the CPUs are being used by ArtRage more and more, which is good. I like the performance at the fastest stable stroke speed. One would expect that during 2, the processors used by ArtRage would be in overdrive... trying to catch up with the stroke... while ArtRage has to do some extra caching of brush positions etc. stroke speed should suffer somewhat...
    It turns out for some reason, the processor use by ArtRage falls DRAMATICALLY... it does not rise (or even staying steady), right at this time when it needs it most. Moreover, a CPU or two will drop out. Is something in Windows interfering with ArtRage's ability to keep performing at full throttle... ?

    Whatever extra work ArtRage has to do to keep track of the stroke... having its CPU use drop at the crucial time has to compound greatly to the amount of lag observed. This CPU use dropping (and some dropping out) seems VERY odd. I would assume all the CPUs would keep working at full performance until it could catch up (if you stopped the stroke or slowed down).



    Here is a screen Grab of the performance dip and ArtRage.

    Note CPUs 1, 3, 5 (maybe 7?) drop out of work with ArtRage ... also says they are "parked"?

    Click image for larger version. 

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  2. #2
    Some algorithms can't be parallelized. The extreme of this is 3D modeling. Some very expensive programs run a single core while doing this.

    It's also common for a program to be increasingly inefficient as the number of cores increases. The more cores to be used, the more complicated the management becomes.

    If Artrage is written in a "managed code" environment, it could be waiting for garbage collection which is not controllable from within the environment. I.e., a dotnet inefficiency.

  3. #3
    Join Date
    Apr 2012
    Posts
    521
    Note:

    For some reason I cannot explain, if the same test is performed with a large brush - 100% or greater, CPU usage does NOT drop... which means ArtRage is getting the most it can from the computer... for those brush sizes: the lag is not so bad compared with the fastest stable stroke for that brush.

    Seems like sizes below 80 all suffer CPU non-use to some extent... accompanied by much the inevitable sharper drop in stroke speed. Of course when the brush is small enough I cannot move it fast enough to cause the lag...
    Last edited by DarkOwnt; 10-12-2019 at 08:11 AM.

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