Optimize!

Is it normal to wait for your computer? Why should I wait 5 seconds when I click on a menu? Why does it sometimes take half a minute to open a new document? Developers, optimize your code, if only as a matter of public service! What about making it a New Year resolution?

Why is my Mac laptop slower than my iPad?

Apple cares about iPad performance

Apple cares about iPad performance

I have a serious issue with the fact that on a laptop with 8G of RAM, 1TB of hard disk, a quad-core 2GHz i7, I spend my time waiting. All the time. For long, horribly annoying pauses.

Just typing these few paragraphs had Safari go into “pause” twice. I type something and it takes ten seconds or so with nothing showing up on screen, and then it catches up. Whaaaaat? How did programmers manage to write code so horribly that a computer with a quad-core 2.6GHz i7 can’t even keep up with my typing? Seriously? The Apple II, with its glorious 1MHz 8-bit 6502 never had trouble keeping up, no matter how fast I typed. Nor did Snow Leopard, for that matter…

Even today, why is it that I always find myself waiting for my Mac as soon as I have 5 to 10 applications open, when a poor iPad always feel responsive even with 20 or 30 applications open at the same time? Aren’t we talking about the same company (Apple)? About the same core operating system (Darwin being the core of both iOS and OSX)? So what’s the difference?

The difference, folks, is optimizations. Code for iOS is tuned, tight, fit. Applications are programmed with severe hardware limitations in mind. The iPad, for instance, is very good at “pausing” applications that you are not using and recalling them quickly when you switch to them. Also, most applications are very careful in their use of resources, in particular memory and storage. Apple definitely cares about the performance of the iPad. There was a time the performance of the Mac mattered as well, but that was a long time ago.

Boiled frog syndrome : we slowly got used to desktops or laptops being slower than tablets, but it’s just plain stupid.

Lion and Mountain Lion are Dog Slow

It's obvious why they called it Lion...

It’s obvious why they called it Lion…

I’ve been running every single version of MacOSX since the Rhapsody days. Up until Snow Leopard, each release was a definite improvement over the previous version. Lion and Mountain Lion, on the other hand, were a severe step backwards…

Lion and Mountain Lion were not just loaded with features I didn’t care about (like crippling my address book with Facebook email addresses), they didn’t just break features I relied on on a daily basis (like full screen applications that works with multiple monitors, or RSS feeds). They were slow.

We are not talking about small-scale slowness here. We are talking about molasses-fed slugs caught in a tar pit, of lag raised to an art form, of junk code piling up at an industrial scale, of inefficiency that makes soviet car design look good in comparison.

And it’s not just me. My wife and my kids keep complaining that “the machine lags”. And it’s been the case with every single machine I “upgraded” to Lion or Mountain Lion. To the point where I’m not upgrading my other machines anymore.

In my experience, the core issue is memory management. OSX Lion and Mountain Lion are much worse than their predecessors at handling multiple programs. On OSX, the primary rule of optimization seems to be “grab 1GB of memory first, ask questions later.” That makes sense if you are alone: RAM is faster than disk, by orders of magnitude, so copying stuff there is a good idea if you use it frequently.

But if you share the RAM with other apps, you may push those other apps away from memory, a process called “paging“. Paging depends very largely on heuristics, and has major impact on performance. Because, you see, RAM is faster than disk, by orders of magnitude. And now, this plays against you.

Here is an example of a heuristic that I believe was introduced in Lion: the OS apparently puts aside programs that you have not been using for a long while. A bit like an iPad, I guess. On the surface, this seems like a good idea. If you are not using them, free some memory for other programs. But this means that if I go away from my laptop and the screen saver kicks in, it will eat all available RAM and push other programs out. When I log back in… I have 3GB of free RAM and a spinning beach ball. Every time. And even if the screensaver does not run, other things like backupd (the backup daemon) or Spotlight surely will use a few gigabytes for, you know, copying files, indexing them, stuff.

Boiled frog syndrome : we slowly got used to programs using thousands of Mac128K worth of memory to do simple things like running a screensaver. It’s preposterous.

Tuning memory management is very hard

Virtual Memory is complicated

Virtual Memory is complicated

The VM subsystem, responsible for memory management, was never particularly good in OSX. I remember a meeting with an Apple executive back in the times OSX was called Rhapsody. Apple engineers were all excited about the new memory management, which was admittedly an improvement over MacOS9.

I told the Apple person I met that I could crash his Mac with 2 minutes at the keyboard, doing only things a normal user could do (i.e. no Terminal…) He laughed at me, gave me his keyboard and refused to even save documents. Foolish, that.

I went to the ancestor of Preview.app, opened a document, clicked on “Zoom” repeatedly until the zoom factor was about 6400% or so. See, in these times, the application was apparently allocating a buffer for rendering that was growing as you zoomed. The machine crawled to a halt, as it started paging these gigabytes in and out just to draw the preview on the screen. “It’s dead, Jim“, time to reboot with a long, hard and somewhat angry press on the Power button.

That particular problem was fixed, but not the underlying issue, which is a philosophical decision to take control away from users in the name of “simplicity“. OS9 allowed me to say that an App was supposed to use 8M of RAM. OSX does not. I wish I could say: “Screen Saver can use 256M of RAM. If it wants more, have it page to disk, not the other apps.” If there is a way to do that, I have not found it.

Boiled frog syndrome : we have slowly been accustomed by software vendors to give away control. But lack of control is not a feature.

Faster machines are not faster

A 1986 Mac beats a 2007 PC

A 1986 Mac beats a 2007 PC

One issue with poor optimizations is that faster machines, with much faster CPUs, GPUs and hard disks, are not actually faster to perform the tasks the user expects from them, because they are burdened with much higher loads. It’s as if developers always stopped at the limit of what the machine can do.

It actually makes business sense, because you get the most of your machine. But it also means its easy to push the machine right over the edge. And more to the point, an original 1986 Mac Plus will execute programs designed for it faster than a 2007 machine. I bet this would still hold in 2013.

So if you have been brainwashed by “Premature optimization is the root of all evil“, you should forget that. Optimizing is good. Optimize where it matters. Always. Or, as a colleague of mine once put it, “belated pessimization is the leaf of no good.”

Boiled frog syndrome : we have slowly been accustomed to our machines running inefficient code. But inefficiency is not law of nature. Actually, in the natural world, inefficiency gets you killed. So…

Optimize!

One thought on “Optimize!

  1. Just to substantiate what I wrote about disk utilization in Mountain Lion : current uptime 13:03 up 5 days, 2:56, 5 users, load averages: 1,29 1,09 1,32. Disk transfers : 400,10GB read, 260,44GB written. So that’s on average 80GB read from disk PER DAY! Practically 1MB per second ON AVERAGE, for five straight days.

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