That's just not true. If inactive memory is something that's already backed by disk (like a memory mapped file), it'll be discarded. Only if it's read-write memory that's /currently held allocated by a running process/ will it be swapped out to disk. Unless you're doing something pathological (like suddenly allocating lots of RAM and forcing paging - what purge utilities do...), the architecture /speeds things up/.
If it's really true that, without doing anything special, things were always being swapped out to disk for you, it necessarily means that there was a process that had allocated (lots, it sounds like) of RAM and written to it, so that stuff had to be paged out to disk to free up RAM without losing data.
It sounds like you were running purge commands or utilities to 'free up RAM'. That is counterproductive. It causes the system to release cached 'clean' (i.e. as already on disk - a mapped file, essentially) mapped RAM and swap read-write memory out to disk, only then have to re-read it all when you actually need it. In other words, using purge 'utilities' actually puts the system into the worst possible state.
I am one of the devs out there running a Macbook Pro with 8Gig of memory (I wish I could have more but I have a 2010 old model). For web development, I have at least Firefox/Chrome/PhpStorm/SmartGit/Mamp/Thunderbird/Terminal/Notational Velocity/Dropbox/Alfred/Sophos AntiVirus open at all times. Now, a long the way, I may open a few other apps that I use rarely, like Photoshop/CyberDuck/VMWare Fusion/iTune/iCal/iOS Simulator/Preview/LibreOffice/Skype. Now, pretty quickly 8Gig gets used up, and the system runs to the ground shortly after.
If I then have VMWare Fusion shutdown for awhile, and relaunch later, the system really just can't take it anymore. The last resort? purge&
At least, that's my day-to-day experience with OSX. Personally, I find the memory management really lousy, worse than other other OSes I used in the past (both Windows & Ubuntu/Fedora/Gentoo).
So why the heck I use Mac still? Because of the driver support is still far better than Linux. With Mac, you are less likely in need of blacklist of some drivers because of freeze up issues.
Either way, I am definitely not a happy camper with the current memory management system in OS X
Your explicit purging is changing the cost of writing dirty data out from an ongoing cost to a single, longer, upfront cost. Instead of writing only when more RAM is required, you're forcing it all to happen at once.
Incidentally, the OS does try to keep an area of free RAM so that some memory can be allocated instantly, it's not only swapping things out when RAM is absolutely full. It's possible though to outrun this process if an app tries to allocate huge amounts of RAM at once though (i.e. more than is kept free for this purpose).
For your specific case, presuming apps are behaving well (see below) you would be better off quitting apps and relaunching them when you need them later. This will free up app the dirty RAM they've allocated (just like when you purge), but the 'clean' inactive RAM will not be purged (because that's not necessary - as I said, it's free to purge that kind of memory when it's needed for something else).
You also want to run Activity Monitor when your system is in it's bad state and see if it's one of the apps you're using in particular that's allocating lots of memory (check out the "Real Mem" column). The OS can't do anything if it's an app that's really allocating and writing to memory, it's obviously not able to just discard this written-to memory.
Really though, if you want to do all those things at once, more RAM might be required. Remember, with VMWare and the iOS Simulator running, you've got two whole other OSes running at the same time, it's reasonable they'd require lots of memory to work well!).
By the way, the purge command was written to simulate /worst case/ conditions when performance testing. It's designed to flush out caches so that the system has to e.g. load all an app's code from disk when launching.
[Source: I worked analysing this kind of thing at Apple until a couple of years ago].
I feel like this is a stereotype that just won't die.
Yes, up till a few years ago you might have to do some poking in /etc to get things working, but as long as you spend a few minutes looking up basic background info before you buy those problems just don't happen these days. I haven't had to edit a config file to get hardware working since 2007.
On a laptop we have here at the office I had to disable a certain driver from loading before a different driver or else the two would squabble over the wifi card and it would never show up.
The other thing that is more software related than hardware is that it is a MS Windows shop, all of the local domains are machine.domainname.local. This conflicts with MDNS as you could imagine, so the Linux machines are unable to access any of the resources on the machines named machine.domainname.local because MDNS would respond with a failure. Had to modify /etc/nsswitch.conf to fix that issue.
Linux is not without its failures. Saying it just works is certainly not the case. Whereas the Mac OS X machines I deploy come out of the box, get configured and are ready to go. Drivers work, software works, don't need to go googling for hours trying to figure out why ping won't resolve a machine.domainname.local address but dig is doing just fine.
I said if you spend a little time scoping these kinds of things out up-front, it's very easy to get a machine on which it will work without issues. Obviously if you found a machine lying around the office and tried to load an OS on it, your chances of it working well are not going to be as good. You can't just load OS X on random hardware and expect it to work either.
Sorry, from my personal experience that still isn't true, as much as I wish it were.
To make a long story short: we could exchange anecdotes all day about the state of 'Just Works' on Linux, but at the end of the day, I think no one with enough experience using various Linux distros and OS X, can honestly and sincerely say Linux is even close to OS X in that aspect.
Myself, I've been using Linux since Slackware 4 and have tried about 10 different distro's over time, alongside OS X for the last 5 years or so. Up to this day, I regularly run into problems that need fixing on Linux, particularly after upgrades, or when switching hardware. Whether it's Wifi cards, USB hardware, multi-monitor support, network configuration issues, software that stops working, system library problems: there's always something. OS X on 3 different machines, from OS X 10.4 through 10.7, I've only had one issue that required maintenance once, on a b0rked upgrade. It was pretty nasty, but fortunately OS X has Time Machine and target disk mode, so in no-time I was able to pull off any important data just to be sure, re-install the OS, restore my Time Machine backup, only to find out everything was back to normal, to the point I didn't even need the files I had to pull before the restore.
However, up to this date, it is not without issues, especially on laptop hardware. Remember that Lenovo ThinkPad T400 from a few years ago? Well, the level of stability from a popular distro, such as ubuntu, has been quite up and down. One release (like 11.04), I had trouble with it booting up and playing nice with dual graphics mode. Today, with 11.10, it is much better. How about that shiny Acer AspireOne 722 netbook? You should check the online thread. There are still discussions about how to prevent freeze up and etc. All these little quirks here and there are the reason why I would still run OS X.
I run half a menu-bar full of resident helper apps, like Dropbox (a big one), Fantastical, ScanSnap, Xmarks (another big one), Transmit (another big one), Evernote, and more. I also keep Apple Mail running, mapped to a half dozen Gmail IMAP accounts. I have "geek tool" updating my desktop with iCal appointments and various ps outputs.
I'm running a local MAMP stack and local Django stack. I run a Parallels Windows 7 VM for testing things in IE and testing from Windows in general.
Other running software is usually Safari, Terminal, Sublime Text 2, Codebox, Source Tree, Sequel Pro, Adium. I run and quit Office 2011 every time I need to edit a document. I run and quit Aperture and Photoshop.
Using this command line to see memory used by processes:
ps -x -o rss,command | awk '{sum+=$1} END {printf "%9.3f %s\n", sum/1024, "MB" }'
Makes me wonder what you're doing to run out of memory.
Here's what I don't understand - why would anyone in their right mind purchase a $2000 laptop and then not spend the 20 minutes and 100 bucks to max out the memory on the thing? It's the easiest thing in the world to do, and basically means you never have to worry about memory usage again.
jerf@jerfhom ~/tv $ uptime
01:01:32 up 2 days, 23:45, 4 users, ...
jerf@jerfhom ~/tv $ free
total used free ...
Mem: 3904192 3682400 221792 ...
-/+ buffers/cache: 740212 3163980
Swap: 6297444 20584 6276860
This is with a respectable Linux dev loadout, but I'm not running my VMs, but that still tends not to strain my system any. $100 on RAM would just be a wasted $100.
My MBP has 8 GBs of RAM, and this is what Activity Monitor tells me:
Free: 2.19 GB
Wired: 1.01 GB
Active: 3.70 GB
Inactive: 1.08 GB
Used: 5.80 GB
2598.480 MB
Active is not like RSS, what Activity Monitor calls real memory is RSS.
That's not a solution, that's a workaround. I'm sitting here with a 4GB RAM machine running Arch Linux with XMonad. I usually run the following applications in day to day usage:
- Firefox Nightly with 50-100 tabs (largest memory hog,
the rest doesn't even come close)
- Thunderbird
- Pidgin
- XChat
- smplayer, which I usually keep open
- deluge
- mpd + ncmpcpp
- half to one dozen of terminator instances with zsh,
most running some text mode applications like vim,
htop or the aforementioned ncmpcpp
OSX is not doing anything "wrong".
I split my time between OSX/Linux and it's pretty obvious to me that Linux is vastly superior in terms of performance, in a wide-range of scenarios. I prefer to use Linux on older and/or memory-constrained systems.
You bring up good points and my article would need some clarification on some parts, I agree on that. I'll just write quick replies back to you, and try to format something on the article itself later.
Purge really did free memory and quite a lot. I'm not too expert (as you probably can tell) how the OS X memory management works, but I mostly settled with solutions that seemed to help my problem. Maybe there was some third party software that messed things up.
The problem with the inactive memory is that it is not freed, it is swapped. So when hitting memory limits of my system, the computer started swapping. Just freeing the memory, in my case, would have been much quicker. Practically my machine was constantly swapping when the memory limit came up. As you said, repair disk permissions caused all this to happen due to filling memory with disk cache. So that was a nice solution to my problem; a way to force swapping on inactive memory.
Python point is bit wrong, I was indeed trying to argue that installing python packages is impossible through homebrew. However, I did use a lot pip+virtualenv, so that's at best a bit vague argument on the OS X side. However, in production I always rely on the packages provided by the OS, not pip + venv, unless really necessary. This is mostly because it makes it easier to keep system up-to-date.
I'm sorry if this showed up as uninformed rant, but I just wanted to share how I felt using OS X and Macbook for a year as my primary computer.