industrial strength UNIX - Flaw??

solrac

solrac

Mac Ninja
One of the main strengths of OS X is supposed to be no memory limitations on applications, right? Every application dynamically requests as much memory it needs, and programs that are not being used end up using no memory.

In fact, an app that has not been used for a while should be paged out of physical memory entirely, right? This is what I heard. Therefore, as many have said here, on OS X you can have like 1000 apps open, never quit them, and never have to restart.

However I find that if I have Photoshop, Illustrator, Flash, Dreamweaver, InDesign, Explorer, Chimera, and a bunch of accessories open, my computer starts crawling.

If I go ahead and quit all the big apps, things speed up. Even if I haven't used those apps in hours.

Why is this? A lot of people said I should never have to quit an app in OS X. Yet it really seems to help.

TiBook 400 mhz, 384 MB RAM, 10 GB hard drive
 
Hmmm...I'm not one who knows for sure, but I think the CPU is still troubled by open apps...
 
First, it does take a moment for applications to get paged out of memory, especially if they were being taxed.

Secondly, you are strongly limited by the amount of memory you have. Increasing yours to 512 would give you a decided performance boost. At lower than that, especially with beefy applications like the ones you mentioned, it's easy to get caught continually paging data from your disk as you switch between them.

Also- don't confuse better multitasking with limitless multitasking.
 
Originally posted by .dev.lqd
First, it does take a moment for applications to get paged out of memory, especially if they were being taxed.

Secondly, you are strongly limited by the amount of memory you have. Increasing yours to 512 would give you a decided performance boost. At lower than that, especially with beefy applications like the ones you mentioned, it's easy to get caught continually paging data from your disk as you switch between them.

Also- don't confuse better multitasking with limitless multitasking.
Click to expand...

What about the scenario where i haven't used any of them for hours at all, yet quitting them still helps? And I would love to get a 512 chip, get rid of my 128, keep my 256, and have 768 MB!!! :-0 :-0
 
I don't think memory is paged out unless a new request for memory is made by another application in the same memory space that's occupied by the first application.

So, no matter how long you let your applications sit, whatever is in the memory stays in the memory unless something else wants some memory -- then the amount needed is paged out.

If you let your applications sit for days at a time, I still don't think anything is paged out unless it needs to be...
 
Originally posted by solrac


What about the scenario where i haven't used any of them for hours at all, yet quitting them still helps? And I would love to get a 512 chip, get rid of my 128, keep my 256, and have 768 MB!!! :-0 :-0
Click to expand...

The fact that you are are not actively using the application does not necessarily mean that the application is not still using the processor.

Open a terminal window and type:
top -u

The "top" command shows cpu utilization and memory usage stats for all running processes. The -u flag tells it to sort by cpu usage.

Right now, I haven't used Word in hours, and don't even have any documents open, and it is still using about 2-3% of the processor.
 
Not all applications are born equal and relinquish processor when no input is coming. Most gooey applications use timer events, which fire irrespective of user activity; this tends to keep them in memory.

Word v.X seems to be the worst offender, as it consumes over 50% of CPU as soon as there is a document open; it drops to a few % when all documents are closed.

I find this word behavior extremely offensive, because it isn't doing anything at the time.

Obviously, all processes consuming CPU are accessing and possibly modifying their memory images, which forces the affected pages back into core.
 
solrac,

Go buy some RAM. It's dirt cheap now. I can attest that more physical RAM speeds up your computer VERY noticably. Check my specs below. My Mac flies for my needs. I typically have ChemDraw Ultra running in Classic, Office X (M$ Word and Excel) open all the time, iTunes, Mail, Mozilla, VueScan X, DesktopCalendar, ASM, LauchBar, and sometimes X48 (HP48GX emulator) and Terminal running simultaneously. I very rarely get pageouts. And, these aplications are cached in memory, they load almost instantly after quitting and starting again. XDarwin (MacGIMP) sometimes causes a few pageouts - depends on how large the image is I'm playing around with.
 
I would assume that since the application (like Word X) is still using CPU power that it's still requesting memory--God only knows what it's doing when it's hidden...tree falls in the forest.

And yeah, 768 RAM is fun :)
But I've got to say that the 2GB on my 2.1GHz I've got on this XP :rolleyes: machine is good too. Keeps it fast, ya know, since it's Windows.
 
Photoshop has a slider in the preferences to adjust how much pyhsical ram it uses. If PSD stil hogs this when you put it into the backgorund and use other apps then that could be a source of slow performance

Word is also abit of a hog in terms of CPU time. Try turning off active word count in the prefs.
 
First of all, when I went from 384 to 512 megs of RAM, I DEFINITELY saw a speed difference.

Second: What amount of free disk space have you got left on your system volume? If the system doesn't have free space to itself, it *can't* use the virtual memory properly. In OS X, the system claims free disk space of the system partition dynamically. You should have at least double-your-RAM free disk space on the system partition. At all times.

Third: Read again your list of open applications aloud. Now imagine an OS 9 user calling in (you're the supporter) and he tells you he's using Photoshop, Illustrator, InDesign, Flash, Dreamweaver and 'some other apps like browsers' open at the same time. You'd laugh at him, wouldn't you? Well, here, right beside you (virtually) is a user with only a slightly better equipped machine (Ti 500, 512 megs of RAM) who's using Photoshop, Illustrator, GoLive and InDesign (all open at the same time) plus Entourage, Fetch, Terminal, Proteus, TextEdit, BBEdit, LaunchBar and Extensis Suitcase (also at the same time with the Adobe apps). I don't see my system crawling. Unless of course Photoshop is applying a filter to a 100 MB picture in the background while I'm importing a large Illustrator clip via clipboard to InDesign. But I think even a Dual GHz Quicksilver would stutter a bit there.
 
Even if you aren't using an application, if it was a window on the screen or in the dock, it's going to get redrawn. Whenever the screen gets updated the OS is going to ask the app to redraw it's window. Therefore it will hang around in memory, or get swapped back in from disk.

OS X's virtual memory is a lot more sophisticated than OS 9's, but if you overload any VM, it'll bog down. OS X handles the bad cases more gracefully, but it'll thrash too.

The bottom line is that paged disk memory is no substitute for the real thing. And apps will take resources (CPU and memory) if you leave them running.
 
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