For a long time my primary workstation was a (now 3 year old) Dell Inspiron E1705, or “bricktop” as ajax liked to call it. However the hinge broke a while ago when I closed my car door while the bag was too close, and when the laptop started to fall apart I decided to get a new machine. Actually, I got two. The first thing I did was get a serious desktop computer, a Dell XPS 630. It’s quite a beast, especially since I got 8GB of RAM with it. I pretty typically have over 2GB of memory used purely for page cache, which is probably my entire working set of files. It’s hooked up to a nice 24″ Dell 1920×1200 monitor. This computer is named megatron.

Needless to say, the machine is fast and nice to use. However, it’s rather unrepresentative of the general personal computing space. So I wanted another machine that was mobile, and also closer to what “most” people use. So I picked up a MSI Wind U123, known as pocket. It has just 1GB of RAM, which is probably the realistic minimum we want to support going forward (ideally we’d be workable with 512MB, and we probably are if you’re just running one application or one or two websites, but…). The machine also has an Intel 945 video, which is also near the lowest end graphics card we’ll be supporting for GNOME Shell.

The difference between the two computers is rather extreme, but I use the netbook very often, and working on it has forced me to optimize some things in the shell. It serves a similar role for performance issues that canaries used to do in coal mines (hence the title of this post). Specifically, I’ve been working on search performance, with fairly good results. We had a few sillies in the old search system like creating lots and lots of ClutterActors we’d never display, not caching lowercased strings, etc. (the other goal by the way of my search work is to move us closer to the current search mockup, which should be cool).

But the biggest performance problem I’ve been running into so far is synchronous I/O. A lot of GNOME libraries like gnome-menus were designed for gnome-panel, which typically you don’t interact with often, and so it’s not a big deal if the process is blocked. However if the shell is blocked, because we’re acting as a compositor, we won’t repaint the desktop or process input, which is a serious user experience problem. An example of this was that we would synchronously stat (check for existence) of recent documents; this could easily take several hundred milliseconds if the data isn’t currently in the kernel cache.

I’ve been reworking our docs handling specifically to be smarter; we use async I/O now, and only stat ones we’re actually going to show in the UI. We could be smarter still, but this has helped a lot. GIO has really nice APIs for this kind of thing.

I mention this for two reasons; first, just because you might be interested in a status update on Shell work. The second is because I’m hoping to Real Soon Now land my extension system patch, so if you create an extension using it, for a good user experience, you’ll need to be very careful about I/O too =)

A major change we’re trying in the GNOME 3 Shell is to be application-based instead of window-based. In this we’ll be in good company with newer releases of other operating systems, but it’s still a major change. What I want to explain in this blog entry is what that means from a user perspective. For the developer perspective, see this wiki page.

Let’s first look at one of the most venerable (and yet apparently still obligatory) applications, the Calculator. In GNOME 2, launching the calculator looks like this:

From GNOME Shell

Launching Calculator

When we click on that menu entry, the application is started (for more details about under the hood, see the linked wiki page above). The visual result is this:

From GNOME Shell

Calculator and the window list entry

There’s a window for the application, and a task list entry. Now in GNOME 2, if we go to the menu and choose Calculator again, we get this:

From GNOME Shell

Two calculators

Technical people will know that under the covers, there are two gcalctool processes, each of which is creating one window. What this example emphasizes is that in GNOME 2, the bottom panel has a list of windows (or tasks), not applications.

Moving on to GNOME Shell, the “window list” and “menus” part are merged into the overview. Let’s take a look at the application well when Calculator is not launched:

From GNOME Shell

GNOME Shell overview application well

Here I’ve added Calculator to my favorites, so it always shows up. It’s not running yet. When I click on it, the active application at the top immediately changes to show that (GNOME techies: this replaces startup notification), and then the widow appears:

From GNOME Shell

Running Calculator in GNOME Shell

So now that Calculator is running, let’s go back to the overview and see what changed there.

From GNOME Shell

Application well, with Calculator running

You can see that the Calculator gained a glowing status indication, like the other applications I had running already. When I click on that icon again, I am switched to the running calculator window:

From GNOME Shell

Looks exactly the same!

In other words, it looks exactly the same, it just shows you the window again. (Under the hood, the program is not re-executed, there won’t be multiple gcalctool processes, etc.)

Ok you say, but Calculator is a pretty boring application and you don’t use it anyways. How am I making your life better? Well, there are two major things.

One of them is that many programs fail in some obvious and other times less than obvious ways if you click the menu entry twice in GNOME 2 (technically, by default this will start two processes). They’ll overwrite each other’s data, etc. For very few instances does it make sense to have multiple if the app is not explicitly designed for it, and this will avoid you accidentally launching two. Personally I get annoyed when I accidentally launch two xchat-gnome instances and appear on IRC twice.

The second improvement here will come when we get a bit better application integration; the mockup we’d like to implement for say Firefox and multiple windows looks like this:

From GNOME Shell

This needs application-specific work though.

As a brief unrelated aside, I think recent Chromium builds with the tabs-in-window borders (technically, client side decorations) looks cool fullscreen in GNOME Shell with the application menu:

From GNOME Shell

Chromium in GNOME Shell

Next post I’ll talk about how GNOME Shell will save you time and get you back into your applications faster.

This work is licensed under a Creative Commons Attribution 3.0 United States License.