Found a significant LR4 speedup - regenerate ACR cache

[jfriend0]

Like many others here, after I upgraded to LR4, my performance went completely to hell.  It would literally take 9-10 seconds just to advance to the next image in the Develop module.  Marking an image for deletion would take 15 seconds.  I'm running a Q6600 - quadcore processor at 2.4GHz with 4GB RAM on Vista 32-bit.  By today's standards, it's not a terrific speed demon, but no slouch either and it worked fine for several years with LR3.  I mostly process D300 RAW files.

After reading a lot of posts here about crummy performance, I wasn't able to find any tips that might help so I started poking around in the preferences/settings.  One thing I discovered was that my ACR cache was perhaps getting starved a bit for size.  It was set to 50GB, but it was on a drive that might not have that much free space.  I reasoned that if the cache couldn't quite be large enough to hold my working directory of images, then it might be thrashing and pretty much never loading from the cache.

So, I moved my ACR cache to a new drive with lots of free space, increased the cache size to 100GB and then proceeded to regenerate the cache for the directory of 500 images I was working on by making a 2 point change in sharpening on all images and then regenerating all previews.  It took awhile to make all new previews for all the images, but after doing so - WOW my old performance was back again, even running on the new 2012 process.  I could move from one image to the next in the develop module in under a second.

So, I don't know if it was low disk space, some sort of general caching problem, a corrupted cache or what, but after making those ACR cache changes, my LR4 performance is back neaer where the LR3 performance was.

[Jim Wilde]

I was used to seeing cache entries in the 17mb range for my circa 25mb raw files. However a few days ago I purged my ACR cache, deleted my preview cache, then rebuilt 1:1 previews. Checking on the cache this evening I was surprised to find average cache entry size well below 1mb, probably about 400k. Just ran a quick test:

Copied 9 raw files, all more or less identical night shots (around 25mb each, hardly any variation) to my desktop. Then imported 3 each into LR2, LR3, and LR4, then checked the cache.

For the 3 LR2 imports, the cache entry was 17,404kb for each one, no variation

For the 3 LR3 imports, the cache entries were 497kb, 942kb, 942kb

For the 3 LR4 imports, the cache entries were 1218kb, 932kb, 327kb

Go figure. I have no idea of the significance of the huge difference between LR2 versus LR3&4.

[areohbee]

Somebody needs to do some benchmarking!