I have Mavericks on an old 24in iMac with a 2,8 GHz Core2Duo CPU and 4 GB RAM. It was slow as molasses there and I thought about going back to Snow Leo on that machine.
[quote]Applications “not responding” (and SPODs - Spinning Pizza of Death - appearing if you don’t have an SSD) getting you down?
Turn off compressed memory in OS X 10.9.x by issuing the following command in the Terminal:
sudo nvram boot-args=“vm_compressor=1”
… then reboot.
To turn it back on, substitute a 4 for the 1 at the end and reissue the modified command and reboot.
I been testing my 4-Gig Mac Mini 2012 by leaving vm_compressor off in OS X 10.9.4 for 5 days without rebooting, and it works like a charm. I’ve got my speed back, and no quick succession of freezing applications (signaled by “not responding” in the Activity Monitor Application) as Memory Pressure just begins to build up after about three days of continuous use.
You’ll know vm_compressor is off by looking at the Memory Pressure Graph under the Memory tab in Activity Monitor - the graph is always a thin red band (because 10.9.x senses page swaps are building up.[/quote]
Now the old iMac is nearly as fast as it used to be under Snow Leo!
So if you have an older Mac then this might prove useful to you too.
If even after compression you need to swap then I guess it is both getting compressed AND swapped all the time which would explain the SPOD all the time.
[quote=113962:@Markus Winter]Partly because they have fast SSDs. The slow HD in the iMac is a major bottleneck.
But I was also going to try it on my newer MacBook Pro which has an SSD.[/quote]
Ok… let me rephrase my question
If it speeds up an OLD computer that doesn’t have an SSD, why wouldn’t it also speed up the latest, greatest, top of the line Mac that doesn’t have an SSD as well?
SSD is still an option in a lot of configs. I have a 2013 27" i7 iMac without an SSD in it.
With 8gig RAM showing 553.5meg “compressed” and ZERO Swap
[quote=113961:@Christian Schmitz]It sounds strange that memory compression would slow down at all. Because if memory is not compressed, it needs to be swapped out.
It must be a very old Mac to have an effect that compression needs more time than writing to disk.[/quote]
2008 I think, so six years. A Grand-Daddy in computing time but still running like an ace and my main entertainment machine due to its 2 TB HD.
Looks like “compression” is used to augment “page swapping”. it kinda “zips” least used files and puts them in the corner instead of paging them to disk… it resorts to page swapping only if/when the compression quota is exceeded…
Previous to Mavericks, it was only page swapping … but the more RAM you have the less often it has to do any of these tasks
and it would be
compress -> uncompress ->compress-> (swap if we pass a limit) - uncompress etc…
My iMac shows ZERO swapping… so it is doing it all via compression for me… which I guess it is faster to compress and uncompress than it is to swap to from the HD
Compressed memory is on a contrary meant to speed up the machine :
Compressed Memory
Compressed Memory keeps your Mac fast and responsive by freeing up memory when
you need it most. When your systems memory begins to fill up, Compressed Memory
automatically compresses the least recently used items in memory, compacting them to
about half their original size. When these items are needed again, they can be instantly
uncompressed.
Compressed Memory improves total system bandwidth and responsiveness, allowing
your Mac to handle large amounts of data more efficiently. Through use of the dictionarybased WKdm algorithm, compression and decompression are faster than reading and
writing to disk. If your Mac needs to swap files on disk, compressed objects are stored
in full-size segments, which improves read/write efficiency and reduces wear and tear
on SSD and flash drives. The advantages of Compressed Memory include the following:
Shrinks memory usage. Compressed Memory reduces the size of items in memory
that havent been used recently by more than 50 percent, freeing memory for the
applications you are currently using.
Improves power efficiency. Compressed Memory reduces the need to read and write
virtual memory swap files on disk, improving the power efficiency of your Mac.
Minimizes CPU usage. Compressed Memory is incredibly fast, compressing or decompressing a page of memory in just a few millionths of a second.
Is multicore aware. Unlike traditional virtual memory, Compressed Memory can run
in parallel on multiple CPU cores, achieving lightning-fast performance for both
reclaiming unused memory and accessing seldom-used objects in memory.
Power Efficiency
The power technologies in OS X Mavericks were built with the capabilities of modern
processors and the demands of modern apps in mind. The new power technologies
work together to achieve substantial power savings, while maintainingand in some
cases even improvingthe responsiveness and performance of your Mac.
These technologies are rooted in a few key principles:
Just work for existing apps. No changes to applications should be needed, though
small changes may facilitate additional power savings.
Keep as many processor cores idle as possible given the demand for CPU.
When on battery power, only do work that the user is requesting or that is absolutely
essential.
As for myself, I will abstain for the moment. All I read in forums around is not very convincing, and am not desperate enough yet to resort to such manipulations.
4 GB is the max for this iMac (even with 3rd party RAM, I checked MacTracker), and I need the 2TB for my movie collection.
Placebo? Well, before it was like “click on menu wait 5 sec select menu item wait 5 sec switch to Safari wait 10 sec ” so the effect here is very noticable.
I"'ll update in a day or two when I have some more long term experiences maybe it will slow down again
Most likely the 4GB of ram had a hand in this… Which if you’re like me and your machine is a 2007 iMac, you’re pretty much stuck with 4GB. Which is the only reason I had to upgrade the machine Otherwise she made a very fine work horse.
I have some doubt turning off memory compression will have any huge effect, even on every old systems. No sure though why Markus has a small boost in speed.
Maybe some (old) background service having issues with compressed memory handling? Or bad RAM modules?
Trust me on one thing: it is not a small boost. The machine was nearly unusable before and now it is very usable again. Having just a few apps running (Safari, eyeTV, iTunes, MPlayerX - it’s my entertainment centre after all) seriously slowed everything to a crawl, and just switching between apps could easily take 10 seconds. Now it is nearly instantaneous again.
I let it run for another day to see if it slows down again, and then will re-enable memory compression again to see what happens then.
Btw the iMac was already slow under Mountain Lion (I had tried Lion but went back to Snow Leo immediately), but with Mavericks it seemed to slow down another 50% at least. So waits increased from about 5-6 sec to 9-10 sec, and the SPOD appeared MUCH more often.
[quote=114070:@Christoph De Vocht]I have some doubt turning off memory compression will have any huge effect, even on every old systems. No sure though why Markus has a small boost in speed.
Maybe some (old) background service having issues with compressed memory handling? Or bad RAM modules?[/quote]
I wonder if it’s because it was swapping out too much in order to try to compress it? Either way, it’s a bit like Windows, if you have a slow PC, turn of the virtual memory in Windows and the machine then become usable. Windows loves virtual memory.
Otherwise she made a very fine work horse.