Performance a bit slow on my iMac (5K, Late 2015)

[bbnck]

Hi everyone,

I recently purchased an iMac 5K 27-inch, Late 2015. It's going great but I have noticed when I have many apps open, animations become really jerky throughout the operating system, particularly in Mission Control and the Dock (e.g. when opening stacks and launching apps). I have been trying to identify what's causing this to see what I need to do, but to no avail. I have been tracking performance in Activity Monitor, and CPU and RAM utilisation is always at acceptable levels. When I am busy and have lots of apps running, I have seen my iMac can use up to 6.7 GB of RAM (out of a total 8 GB), but memory pressure always looks normal. It has never gone above 40%.

If these performance issues are simply occurring because I need more memory, I don't have a problem buying more - but what I am seeing in Activity Monitor suggests otherwise. I called AppleCare about this and they asked me to perform a PRAM and SMC reset but that made very little difference. I also tried a complete re-install, no change. After going through with them what I can see in Activity Monitor, the representative advised me to consider upgrading the memory in my iMac to help with overall performance. She was convinced it is due to a lack of memory, but if that is the case, why do I still have over 1 GB free (according to Activity Monitor) and memory pressure is always normal? I am prepared to pay for more memory if I need it, but I want to at least be partially confident its the cause of these performance issues before I buy, and the AppleCare representative did not convince me it is.

So I am hoping someone here can help me. I have attached an EntreCheck result log to this post in case that proves helpful to anyone.

Thanks!

View attachment etrecheck.txt

 

[harryb2448]

For the very breasons you state bbnck I went with the flash drive option. Suggest at least 16GB of memory and how often do you reboot the iMac? Next question I trust you are not running AV software which can have a slowing affect as these are real resource hogs.

 

[chscag]

Buy the memory. You should be running with 16 GB if at all possible. And why didn't the Apple Care rep convince you? The first thing I did with my 27" iMac when I purchased it was up the memory from 8 GB to 16 GB.

 

[Slydude]

With several apps open and that makes sense. Can you give us an idea of what apps are open when the problem starts and what you're doing?

 

[pm-r]

but memory pressure always looks normal

Unless it all just green, but if any amber or red showing, then you'll have some slowdowns.

Having 16GB RAM should give you some definite improvements as already mentioned.

 

[ron4mac]

So I am hoping someone here can help me. I have attached an EntreCheck result log to this post in case that proves helpful to anyone.

There are notes about killed processes due to insufficient RAM.

Also, I've recently identified some issues with my VirtualBox entensions (.kext). You could disable them (and maybe the FitBit one) to see if they could be affecting performance.
Move /Library/Application Support/VirtualBox to /Library/Disabled/
Then reboot and test. If no change, move them back.

 

[bbnck]

Hi everyone,

Thanks for your responses. OK, I am starting to believe a RAM upgrade is in order. I've been fine on 8 GB RAM on a number of machines but maybe having an SSD on my Windows computer has spoiled me into thinking it's enough when it might have been paging without me noticing. To achieve the best performance, is it advisable to get 8 x 4 GB memory modules (which would replace the existing 2 x 4 GB modules in my iMac) or 2 x 4 GB memory modules to install in the 2 free memory slots, or is the difference trivial?

Next question I trust you are not running AV software which can have a slowing affect as these are real resource hogs.

No, XProtect and common sense seem sufficient for most people, so is for me too.

Also, I've recently identified some issues with my VirtualBox entensions (.kext). You could disable them (and maybe the FitBit one) to see if they could be affecting performance.
Move /Library/Application Support/VirtualBox to /Library/Disabled/
Then reboot and test. If no change, move them back.

Regardless of whether or not VirtualBox is affecting performance, I haven't got much choice either way as it's the only free option to create Vagrant VMs as far as I am aware.

Unless it all just green, but if any amber or red showing, then you'll have some slowdowns.

Memory pressure has always been green, even when I've got a lot running during a busy work day.

 

[chscag]

Why spend more money than need be? Just buy 2 x 4GB modules and populate the free slots. That will give you 16GB.

 

[bbnck]

Why spend more money than need be? Just buy 2 x 4GB modules and populate the free slots. That will give you 16GB.

I don't want to spend more money than necessary, but I am interested in knowing if there is a performance cost in using all four memory slots versus just two.

 

[harryb2448]

When we purchased our iMacs, had the option of a 7200rpm hard drive, a fusion drive and flash storage. Sadly the 7200rpm is by a long shot the slowest of the three, and the fusion has only 24GB of flash on this model, not large enough for the operating system. To me this left only one option Flash Storage, which is much faster than the SSDs. What I think you are seeing is the difference between your Windows machine with SSD to a standard 7200rpm drive. Memory will help to a limited extent.

 

[chscag]

I don't want to spend more money than necessary, but I am interested in knowing if there is a performance cost in using all four memory slots versus just two.

None. Go ahead and purchase the 2 x 4GB and you should be OK. Of course, you can always opt for more than 16GB as your machine can take up to 32GB of memory. But that's up to you.

 

[ferrarr]

If you are adventurous, you can take a look at fixit.com, to see if replacing the internal hdd, is worth the time to replace with an sad.

https://www.ifixit.com/Guide/iMac+Intel+27-Inch+Retina+5K+Display+Hard+Drive+Replacement/30522

 

[bbnck]

If you are adventurous, you can take a look at fixit.com, to see if replacing the internal hdd, is worth the time to replace with an sad.

https://www.ifixit.com/Guide/iMac+Intel+27-Inch+Retina+5K+Display+Hard+Drive+Replacement/30522

Definitely not feeling adventurous with replacing the hard drive with an SSD on this iMac. Requires complete disassembly - I'll no doubt end up breaking something which is a risk I don't want to take.

What I think you are seeing is the difference between your Windows machine with SSD to a standard 7200rpm drive. Memory will help to a limited extent.

Perhaps, and I do certainly notice the difference in launch times and so on, but I do notice system performance on my iMac to be much faster than my Windows computer with an AMD Athlon X4 860K processor. Here's what is interesting though: if I lower the resolution on the display (e.g. to 2048 x 1152 or 1600 x 900) when I am running lots of apps, the animation lag goes away completely. This suggests to me it's either caused by a shortage of memory, the GPU being inefficient to handle the HiDPI resolution or Apple not optimising their software well. If it's the GPU, I dread to think what the iMac 4K is like with its integrated GPU.

I realise an SSD makes a huge difference to overall system performance, but any computer with a mechanical drive should still perform acceptably. It's boot times, app launches and other I/O tasks that are noticeably faster, and can certainly give the impression that a computer is more powerful than it really is.

I'll update this thread once I've upgraded the memory to 16 GB to see if that helps. I'm hoping it does.

Thanks.

 

[pm-r]

I don't want to spend more money than necessary, but I am interested in knowing if there is a performance cost in using all four memory slots versus just two.

Very very doubtful, or so small you'd never notice, but for that Mac model, do install the RAM modules as matching pairs!! That willand can make a difference.

 

[pm-r]

To me this left only one option Flash Storage, which is much faster than the SSDs.

Ahem…really?? And in an iMac???





- Patrick
======

 

[bbnck]

OK, I think I can safely conclude by now it is definitely being caused by a shortage of memory. I've just caught memory pressure at the warning colour.

Very very doubtful, or so small you'd never notice, but for that Mac model, do install the RAM modules as matching pairs!! That willand can make a difference.

I've purchased 2 x 4 GB modules, as my iMac currently has 2 x 4 GB modules installed. I assume that is what you are referring to?

 

[pm-r]

I've purchased 2 x 4 GB modules, as my iMac currently has 2 x 4 GB modules installed. I assume that is what you are referring to?

Yup.

See Apple's install guide if needed:
https://support.apple.com/en-ca/HT201191

PS: Looks like you caught its memory misbehaving red handed, or should that be amber handed???






- Patrick
======

 

[harryb2448]

Yes flash storage in an iMac. Maybe the new has not travelled to the frozen north - as an option since the late 2012 model. Yopu are a doubting Thomas Patrick.


http://www.tedlandau.com/slantedviewpoint/index.php/archives/2016/1878

 

[pm-r]

Yes flash storage in an iMac. Maybe the new has not travelled to the frozen north - as an option since the late 2012 model. Yopu are a doubting Thomas Patrick.
http://www.tedlandau.com/slantedviewpoint/index.php/archives/2016/1878

I was referring to your earlier comment

To me this left only one option Flash Storage, which is much faster than the SSDs.

as we treat flash and SSD storage as almost basically the same thing up here.



- Patrick
======

 

[harryb2448]

Poor things they ain't. SSD is a hard drive, flash is connected via PCI-E.