@Danas_Anis you’re going to need to provide way more details than that. Can you find the darktable log and post it, along with OS and dt version details?
If you did not update Darktable or change some config in the software, then maybe, Darktable just shows the symptoms of another problem in your computer.
Have you found other softs that seems slower or other problems ?
In my case (Windows, DT 3.2.1) the export to jpg takes minutes, not seconds.
Hardware used? OpenCL enabled/disabled? Modules used (denoising, masking)? …
There is a large number of parameters influencing the time needed for processing/exporting images. Without having any information on this parameters it is impossible to give any qualified support.
There is a debug option (-d perf) for dt which can be used to analyze in detail where dt needs how much time (see manual for further information).
I am doing further investigation, I may be having a HDD fault, which results in Darktable to behave slow, other software is having slowdowns with files from that HDD as well.
OpenCL - not available
Modules used: exposure, filimic, local contrast, denoise (profiled), sometimes tone equalizer.
It is slow independently of modules used, but the biggest impact seems to have denosie and tone equalizer, which does not come as a surprise.
It is probably related to my old HW (i5 @ 2,7GHz, 4G RAM).
Still, all this waiting to get a JPG is not discouraging me from using DT 
I use darktable with 4 GB, but with an NVidia card and OpenCL support. Without tone equalizer and dehaze in ‘local average’ mode, performance is not an issue. denoise profiled, filmic, LUT 3D etc. A 16 MPixel image is exported in about 10 seconds, 2.5-4 of those are taken by the ‘Amaze’ demosaic.
More memory is better, but simply adding 4 GB more if the machine is not using much swap AND not using tiling too much won’t make much difference, I think. I’ve increased the tiling limit from 500 to 1000 MB, now I don’t get tiling in ‘Amaze’, and it still takes 2.6 seconds 
@AdamD: If you can live with lower-resolution exports, you may try entering an export size limit (such as 1920x1080 for FullHD, or whatever you prefer/need) in the export module and disable ‘high quality resampling’. Try exporting a few images with high quality en- and disabled. If you see no difference, I think you’ll be happy about the performance boost.
Which CPU is that, where Amaze needs 2.6 seconds for a 16MP File?
On my 8 years old AMD FX8350 CPU Amaze needs 0.19 seconds for a 15MP file (measured in RawTherapee)
Core2 Duo E6550, 2.33GHz 
https://www.cpubenchmark.net/compare/Intel-Core2-Duo-E6550-vs-AMD-FX-8350-Eight-Core/941vs1780
Anyone using dt on a laptop with Intel uhd graphics, or a new ryzen 4000 apu? Does opencl work ok on these?
Specifically in thinking of Acer Swift 3 with ryzen 4500U.
The intel/beignet implementation of OpenCL is blacklisted for darktable (darktable/opencl_drivers_blacklist.h at master · darktable-org/darktable · GitHub). So I assume OpenCL will be diabled for intel (uhd) graphics cards. For Ryzen 4500U I don’t know, but this APU contains only 6 GPU cores. Even if OpenCL is supported I would not expect a great performance boost (this is an assumption without having experiences with this type of processors).
Aww. So a thin and light ultrabook is not a good option for dt. Will have to start browsing through gaming laptops.
You can also look at eGPUs.
Yes, a eGPU migth be a solution to power up a low performance laptop, particular considering that you can run into temperature problems if you highly stress a (not optimally cooled) laptop with computational intensive tasks.
AdamD, I don’t know if you can install opencl on windows, but I know on Linux the difference with/without is quite significant (basically, for me I can use the external GPU or not)
Intel integrated UHD graphics: Yes, openCL works. At least it does for me. Asus Zenbook flip UX360UA, Core i5, Skylake GT2 [HD Graphics 520], linux mint 20, darktable 3.2.1.
Thin and light laptops are an option, may run hot at times (the above gets up to around 55-60K when exporting). Before you purchase, check on the quality of the screeen in terms of % coverage of sRGB/ Adobe RGB and screen brightness. A while ago I was thinking of upgrading to a Zephyrus G14 but decided aginst it as the screen brightness wasn’t great.
EDIT I just looked at a different review of the G14 and the screen came ot pretty good…time for another look.
Would be great having a laptop working at 55-60 Kelvin…, but I greatly fear that you meant 55-60 °C 
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The G14 and G15 have good screens, and are quite thin and light. It’s the cheaper A15 that has a poor quality screen.
Oh yes. Oops no liquid helium cooling here. It does get higher tho, I had it up to 92 centigrade streaming a 4k video (in 4k) from youtube on a hot day. Measured by output from “sensors”.