Really poor performance on iMac - swap is out of control

I've got a Late 2015 iMac (4GHz i7, 16GB RAM), which I expected to be really powerful. Actually, in benchmark tests, it did slightly better than my old 2009 Mac Pro! However, I'm really disappointed with the performance I'm getting out of it. I'm trying to figure out if it's the computer itself, or Adobe Creative Cloud.

So, the pattern I've noticed is that swap RAM tends to go way up even before the system has come close to exhausting the 16GB of hardware RAM. I'll run the htop command to watch the memory stats, and after a clean reboot, swap is at 0 or close to it. Working in Photoshop for a while, the swap starts to go up and eventually goes as high as 12GB, even though—like I mentioned before—the hardware RAM is still significantly below 16GB.

I put Photoshop in low-res mode (so it doesn't run in retina), and this helps quite a bit. The iMac can run maybe 3-4 days longer before swap is up at 10-12GB and everything on the computer starts running more slowly.

This is extremely frustrating, and I'm not sure what to do about it. I don't know i

iMac (Retina 5K, 27-inch, Late 2015), OS X El Capitan (10.11.5)

Posted on Jun 29, 2016 12:26 PM

16 replies

notcloudy

Level 4

1,258 points

Jul 4, 2016 1:03 PM in response to CaptSaltyJack

CaptSaltyJack wrote:

The thing is, I've put the same amount of workload on my 5-year-old MacBook Air, and it runs better than a 2015 iMac under the same conditions (even less RAM on the MacBook Air, too - 8GB). This is why this is so befuddling. But I'm guessing because the iMac is 5K retina with such a higher pixel density, that everything I run on it is more demanding than it would be on an older MacBook Air.

So if I up the RAM from 16GB to 64GB, I'm guessing that will solve these issues?

If you updated all your software - you are not running the same workload.

Programmers are not taught to be efficient - or to consider what else is running at the same time -- so software can be inefficient - swapping may occur because of the construction of the program.

Again - biggest change is in how RAM is used in Yosemite and El-Capitan -- so it may be your software just doesn't play well together.

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Really poor performance on iMac - swap is out of control