Performance Problems: Difference between revisions

Revision as of 16:23, 4 February 2020

This applies to MXWendler version 4.2 and above

There are five different bottlenecks that have to be passed for perfect video playback:

Disk:

Videostreams are something from 1..100MB/s, and do not forget that having two or more streams reduces the throughput much more because of a permanently moving disk head.

Am i disk limited?

Open several streams at the same time until the CPU usage does not grow any more. You reached the maximum throughput of your disk
Best disk performanceUse a disk array. Use fast disks ( >= 10k rpm ).
Use SSD, use SSD in arrays, they perform up to > 500MB/s, as seen on a Mac Pro with 2 Crucial SSDs on Raid 0

RAM

Enough fast RAM is very important for MXW. Normally computers systems have enough RAM ( >2 Gig, 4 for Mac ) today, so this is generally not a likely source for performance problems

CPU

MXW is heavily multithreaded and will use every core that your system has to offer. But there are some situations where CPU-intense tasks cannot be parallized, eg. creating and opening many movies at once or decoding very large videos ( >=4K )

Am i CPU limited?

Open the task manager.
On modern multicore systems, the real situation hides behind the figures: if you cannot parallelize a task, and a single core cannot handle the problem in realtime, you are CPU limited.
Open eg. a movie >= 4k ( with demanding content! ) and if it does not play in realtime AND you see a CPU use of ca. 25% on a 4-core system, you are cpu limited.
Or play a movie ( at best with sound ) and while it is playing, constantlly open and close other clips. If the first movie starts jittering, you are CPU limited.
The solution is to get a faster CPU ( where MHz are in this case more important than the number of cores ) or - most of the times easier - reduce server load, eg. split videos, combine outputs, reduce resolutions etc.

GPU

MXW renders 100% on the GPU, no pixel colour is touched on the CPU side.
The performance of GPUs varies widely, some GPUs have 4 pixels processors, some have 1000. If you have a recent model ( bought since 2009 ), you should not experience too performance problems on GPU side. But there are important limits, most noteably GPU RAM, this means, the dedicated GPU RAM built onto the graphics device. If you run out of GPU RAM, there will be a severe performance loss. A lot of GPU RAM is used when there are

- - many images open
- - images with very large sizes open
- - many effects used
- - extreme large output sizes

Am i GPU limited?

GPU limitation is reached, when it takes very long time to open eg. dialog boxes.
Reduce the output size. Use less effects. Delete some images, delete some videos. If the performance rises, you are GPU and/or GPU RAM limited.
A solution may be to rework your visual setup.

- - use only the resolutions you need
- - keep resolutions below certain limits, especially Power-Of-Two limits.

Under NVidia, disable for optimal performance:
- - anisotropic filtering
- - antialiasing
- - texture filtering

Use 'Single GPU Performance Mode' in combination with a Matrox to split the video output.

Be sure your keystone setup ( in fact, this is geometry ) is not too complex for your graphics board.

System Busses

Video data has to be carried from the disk to the cpu to the graphics card. At each stage, the video is decompressed, and the data stream will take more bandwidth.
- - be sure that your disk bus is as fast as the disk. There is no point in connecting a fast RAID to USB 1.1
- - Have fast memory and a fast mainboard. Mac Pro is a reference design in that area.

Monitors

You cannot change the performance of your monitor, but you should take care that your whole system is in sync at a common base frame rate. In Europe this is 25 FPS:

- - the video is rendered/produced in 25 fps
- - the video engine runs in 25 fps
- - the monitor has a refresh frequency of 75Hz