AviSynth+ thread Vol.2

[tormento]

Do we still need to declare SetMemoryMax?

I mean, almost 70% of the computers are now 64-bit with gazillions of GBs of RAM.

Is it of any use? Can't we simply let modern Windows to manage memory?

[LigH]

You can probably omit it quite safely. Avisynth uses a convenient default.

[Boulder]

The default is quite conservative and is sometimes not enough if you work on 4K sources with heavy filtering and use multithreading. There's no real harm setting the max higher if you have the memory available, Avisynth will use what it needs and not all of it automatically.

[tormento]

Perhaps I didn't explain well.

I know I can set it as I want but, seen VaporSynth memory use, why can't AVS+ go that way too and send Setmemorymax to ancient memories?

[tormento]

Originally Posted by Boulder

The default is quite conservative and is sometimes not enough if you work on 4K sources with heavy filtering and use multithreading.

I can't find my post but, some years ago, I did some tests where I saw performance decrease with Setmemorymax increase.

[FranceBB]

Originally Posted by tormento

I know I can set it as I want but, seen VaporSynth memory use, why can't AVS+ go that way too and send Setmemorymax to ancient memories?

It's already ancient memory.
There's no need to set it, Avisynth will manage that automatically.
By default, in modern x64 systems, it will use 4GB of RAM which is plenty.
Remember that this is the memory of the cache, in other words the memory used to store frames without having to fetch them again, NOT the RAM used by filters in general. This means that even if you were to set SetMemoryMax(512) but you were heavily filtering a UHD content, Avisynth would still use way more than 512MB of RAM. Remember that the cache is there only so that if you have temporal filters and encoders that need to access frames in a non linear fashion, Avisynth won't have to compute them every single time it moves forward and backward and forward and backward etc. The bigger the cache the more frames are gonna be stored, but storing too many frames can be detrimental as it's gonna use RAM that could otherwise be used by - let's say - the encoder, which is why the cache size is calculated on the fly on the basis of the available RAM and it never exceeds 4GB.

Assuming RGB48 (which is overkill anyway), we have:

3840×2160×48 = 398131200 bits = 0.0498 gigabyte

That's just for one frame, so at the current default Avisynth can cache more than 80 frames. Obviously working with RGB48 UHD is a bit unrealistic, but if we work in YUV that number increases and it even goes much further if we work in 8bit and at lower resolutions.
My point is that it's already implemented correctly and I don't see a reason to change that. If anything, having the SetMemoryMax() is useful if you wanna reduce the cache.

[DTL]

It looks you not understand how frame-based AVS+ MT is working.

To make things as fast as possible (to minimize CPU stall on threads sync) it looks AVS+ simply put several frames cache around _each_ filter in the filtergraph and in _each_ logical thread. So any time system have some free logical CPU cores it can load it with some useful computing.

But it cause awful RAM consuming in any 'complex' scripts of a several filters in a chain.

Total RAM in a cache is about NumFrames_in_Prefetch_x_NumFilters_x_NumThreads_x_FrameSize.

[Boulder]

Regarding the 4GB, which is unfortunately not enough in many cases: https://forum.doom9.org/showthread.p...75#post1913375