Back on Linux (after one year of Apple and OS X)

I don't even know where to start with the author's complaints about the memory model. Inactive memory is not "memory from a recently used app". Inactive is just like active memory. It is not unused memory. Inactive memory is memory that has not been accessed recently and will therefore be swapped to disk first. Just like active memory, it can be be freed immediately if it has not been modified (eg. a memory mapped file, or a local copy of some shared memory), but if it has been modified, it must be paged to disk because otherwise data would be lost.

All the purge command and "Repair permissions" do is swap out lot's of memory. But this is not unused memory. This memory will likely be paged in again sooner or later. It does not help much if you simply have too little memory. That's why the author claims he has to run the commands again and again. But the problem is not the broken memory management system. The author simply has too little RAM.

Which leaves the question: Why does Mac OS need more RAM than Linux?

Well, there's the simple fact that there is much more stuff running in the background on Mac OS. You have automatic indexing of every file on your hard drive and file system monitoring. Try downloading an app that opens some file type. The moment it is unzipped, the Finder automatically uses it to open supported files.

Then you have an automatic version control and backup system running in the background, for every single file on your hard disk (Time Machine). Additionally, many Mac apps aggressively cache data in memory. Take iTunes. You can scroll lag-free through music libraries with tens of thousands of songs and their album artwork, and filter them instantly.

These things use up RAM. Lot's of it. And that's why you can't run 3 VMs on your Mac if you only have 4GB.

If you don't want the extra features / bloat of Mac OS please go ahead and use Linux. But don't write a completely ignorant piece about how you think the memory management model in Mac OS is broken without reading the real docs: https://developer.apple.com/library/mac/documentation/Perfor...

I wouldn't mind the official end of life of linux software.

I used to be a window maker user (always hated KDE and did not like Gnomes sluggish performance). Window maker is nowadays not even on the DVD distributions. But it still works fine although I think nobody has really touched the code since long.

That is one of the nice things about linux compared to OS X. On linux dead software will still be alive for long and you get it via your favorite package manager. On OS X dead software is really and finally absolutely dead.

Okay, I really think you know much more about memory management than the writer of the original post, the question for me is using chrome with a few tabs (8 for example) and Dropbox besides the default applications I face huge slowdowns (the system becomes unresponsible for a few minutes), the same happens with Safari, for a system that was described for me as "it just works" this really sucks. This with 4GB of RAM in my MacBook Pro.

I face no such problem with Linux or FreeBSD in the same hardware.

I think the problem is that you used OS X for a year. I've been using my Mac for 4 years, and Linux for another 4. And I have Python (in fact I have at the same time Python 2.5, 2.6, 2.7, 3 and 3.1 for testing purposes), I have installed so many packages I already lost the count. You only need to be sure the path is correct when doing it. And I have 2 Gigs of RAM. Mac OS can be a bit hungry, but there's an "easy" solution for this. Closing unused applications. That bright dot in the dock means something is using an incredible amount of RAM just to sit there doing nothing. If I only leave open my mail app, Chrome, emacs and twitter client, I can go for days without ever hitting the disk cache. If I start adding more things (or tabs like I'm crazy), I'll hit the cache, of course. But this also happens in my Linux systems, it's not a Mac OS problem. As for the DVI port... I usually leave the DVI adapter linked to the monitor I use. And use bluetooth devices when possible. So far only once I have used a hub to connect 3 things to my Macbook (an SD reader to copy images, my Ben Nanonote to install some packages and my iTouch to sync with iTunes). Happened once, in 4 years (and I also have a drawing tablet, btw).

A well constructed reply. I probably will not be as organized but here goes:

Certainly OSX is becoming a lot more open in some respects. There are clearly some people in Apple that have been trying to make some changes for a while, and I applaud that and hope to see it continue. The fact they ship with a lot of major open source tools makes me happy.

Even on my side of the fence I will go as far as to say there are plenty of tools in OSX to meet most needs of most developers.

Also a window manager is not "low level" in the traditional sense. I could of worded that better. It is however something at a lower level than one can have any control over on OSX. If you choose OSX you _must_ accept Apple's choice of window manager. I on the other hand use Awesome, a tiling window manger with a Lua driven UI which allows me to edit just about anything in the UI and reload it on the fly without logging out. Typically everything runs in a single process that consumes well under 20MB of ram. That's the kind of control that OSX does not offer. Sure it is not "low level" but it sure feels that way on OSX when you can't do anything about it no matter how much you program, it's simply outside of the range of what the platform allows short of hacking binaries or running an XServer on top of the existing OSX desktop.

As for memory management I would expect any novice linux sysadmin _should_ know how to go through and kill all unneeded processes, run headless, build a lean kernel tailored to the hardware etc. I make even interns learn how to do things like these. Any professional sysadmin should also know how to build in extensions like PaX or selinux, and recompile any user-land binaries as needed to to support it. For sensitive systems you can also build a hardened toolchain and compile every single binary on your system through it. This means you can force position-independent executables, stack smashing protection, and compile-time buffer checks, which can prevent a lot of 0days in other people's code that might otherwise work with "virgin" binaries. I do all of the above for all my production systems. I also at least always compile my kernels with Pax which randomizes memory addressing schemes at compile time. This way as well so kernels will map memory the same way for added protection against many 0days which will often assume stock memory mapping.

There are lots of things you can really only do to protect a system, if you have all the code sitting there. In OSX you just have to cross your fingers there are no 0-days in any system processes, or that if there are... that apple gets around to fixing them and deploying them fast.

In regard to ksplice, your right. I said enterprise here for a reason. Most sysadmins won't touch it for most uses. People that do know what they are doing with it however and can't afford downtime make use of tools like these to keep boxes online, and even can justify far more frequent kernel updates than they might ordinarily. In OSX you don't even have the possibility to do such things. Most system level updates require a reboot, period.

in response to OSX running better on non-apple PC hardware than Linux... I am hard pressed to buy that without more detail of your exact issues.

Homebrew... Homebew is neat. Truly a step in the right direction. Every OSX install I do, It is the first thing to go on. It only has perhaps a fraction of a percent of the number of packages in a modern Linux distribution, but it at least has a lot of the important command line tools. I really hope this project matures and gets more community support to bring a wider range of open tools to the table. I used macports for a while but broken packages at every turn made it rather unusable.

Regardless, it is still just a fledgling effort. Personal use? Sure, but I would certainly not trust it for a production system. Many packages are very out of date, or are having to deal with the most recent OSX-compilable builds. It's better... but they have a long way to go yet. I do welcome anything encouraging more open source adoption without the OSX crowd though.