Is Yosemite suffering from poor scrolling performance?

Yosemite IS suffering from poor scrolling performance (also on official hardware)

EDIT: See post #4 for testing instructions and conclusions: http://www.tonymacx86.com/general-h...g-poor-scrolling-performance.html#post1085381

I've noticed a lag when scrolling in Yosemite that wasn't present on older OSX versions (Lion compared here). In this video first a 2011 system with Lion showing smooth scrolling. Note that the handlebar always keeps up with the mouse. Then a 2015 system that is more powerful but has Yosemite instead. Notice the much less smooth scrolling and the handlebar that lags behind the mouse when moving quickly.

When scrolling in Lion, CPU use of mail.app never goes over 50 percent. When scrolling in Yosemite. CPU use of mail.app goes to 100 percent!!!

Scrolling smaller lists is less obviously lagged but the faster you scroll or the more items in the list, the more lag. When CPU use during scrolling reaches close to 100 percent lag is induced. This means, I assume, that something is processed during scrolling in Yosemite that wasn't in Lion which is apparently very inefficient.

The list being scrolled is a big list of my Gmail. For a long list, try console although it's not as pronounced there as in mail.app. Check how well the handlebar keeps up with the mouse when doing quick moves as well as CPU use when doing so repeatedly.


Example video with poor quality due to compression but look closely at how the handlebar follows the mouse pointer. In the first part it follows perfectly and the scroll is smooth. In the second part the handlebar has to chase the mouse when moving quickly and the scrolling isn't as smooth anymore.

Anyone else noticed this? I assume it's just per design due to the new transparency and visual candy or what not, but it's not very nice.

Video url: https://www.youtube.com/watch?v=vcsPlv3ilv8

[video=youtube;vcsPlv3ilv8]https://www.youtube.com/watch?v=vcsPlv3ilv8[/video]

Hi there,

I'm having the same issue. I've posted this problem today and nobody seems to have a response or answer. I installed Yosemite on my Mac Mini to see if the same problem was there and it was!

My specs are:

Rampage IV Extreme, i7 3930k, GTX 580 3 gigs

Hope we can find a solution!

Best, Miro

Very interesting. What osx was on your Mac mini before and how was scrolling on that version? I've only confirmed that Lion was free from the issue, I don't know when it came along. Suspicion is that it came into being when the transparency stuff was added to osx. If you look carefully at the top border of apps when scrolling, there is a very slight coloring effect when scrolling. When scrolling fast this effect is updated fast as well. This could be poorly coded and inefficient for large lists.

In my experience it's primarily larger lists that has the issue. I've also noticed that disabling transparency in accessibility doesn't affect the lag at all but this may be due to the fact that the graphic code isn't removed from the calculation, only the end result. Can you confirm this on your Mac mini as well?

Other observations: scrolling in Chrome isn't affected. Chrome doesn't support transparency in its window. Scrolling the thumbnails to the right in a preview window of a pdf isn't affected either. Note: not the actual pdf content but the thumbnails of pages to the right. I never checked but I assume this sidebar isn't affecting the transparency of the window either.

An interesting note is that the user interface test in xbench performs horribly on Yosemite. This may be related to this.

Yosemite IS suffering from poor scrolling performance, including official hardware.

I decided more testing is needed to rule out isolated cases. I upgraded my maxed out iMac 2011 to Yosemite from Lion to look into how it behaves. It turns out the official iMac suffers the exact same issue as all the other computers that I've tried. It's even slightly worse than my hackintosh, obviously due to the stronger CPU in my hackintosh. My Air 2015 performs worse than the iMac and that of course has an even weaker CPU. It seems to be related to the CPU as to how bad this issue gets but no current computer can give you a completely lag-free experience. I base this on the fact that the CPU in my hackintosh has the strongest current single-thread performance, and whatever processing happening during scrolling is single-threaded according to Activity monitor.

I also ran the "User interface test" in Xbench on my iMac to compare the score with Lion on the same computer. It turns out that the score took a gigantic hit, falling down to 42 points on Yosemite from a blazing 192,6 points in Lion. This test result is clearly related to this issue. One could argue that this means whatever processing is being done during scrolling is something that engulfs the entire user interface in Yoemite, thereby bogging down the Xbench score. Maybe scrolling is just the most (only?) noticeable area to the user.

I've been looking over options to remedy the situation. Disabling transparency in the accessibility settings does nothing for scrolling performance, nor Xbench score. This goes against all the recommendations to enable this setting for older computers. The gains reported from this may perhaps just be placebo? No other setting I've found will help and since it's an issue on what I assume is all official hardware I fear there's little we can do here.

Reported official computers so far having the issue:
Macbook Air 2015
iMac 2011 maxed out
Mac Mini (unknown year)
And of course, hackintosh builds.

I'm going to try finding an official 5K iMac to test as that's the strongest official hardware for single-threaded apps, but I doubt that I'll see any difference. The Air 2015 is even newer than the 5K iMac and it's still suffering from the performance hit.

If you want to test your Yosemite mac/hackintosh for this, go this route for the least subjective result:
- Open up console.
- Make sure that you have about 4000 log entries as shorter lists up to about 1k or so will not trigger the bug to a level that it's very visible.
- Click and hold your mouse on the scrollbar handle. If this isn't visible, scroll for a bit to make it visible.
- While holding the scrollbar, move your mouse up and down the reach of the scrollbar. Try slow sweeping motions as well as quick moves.
- If your scrollbar handle always sits tightly in line with your mouse pointer, you're not suffering from the issue. If however the handle lags after the mouse as if there was a rubber band between them you are affected. You can see an example in the video posted in #1 if you look closely (it's grainy and overcompressed).
- Also look at cpu use in activity monitor while continually scrolling vigorously in the console window. If you see CPU use close to 100% you are affected. On none-affected systems CPU use should never climb near this high during the scrolling. When reaching 100%, the lag sets in as the CPU can't keep up with the required processing for lag-free scrolling.

What we do not know is:
- ALL official hardware seems to be affected.
- With what OSX version this appeared, but I'm assuming Yosemite.
- If there's anything we can do about it, once again, I assume no.

EDIT:

Tested this on an official iMac 5K with the same result. Clearly all hardware is affected.