On a fresh install of Slackware64 14.1, I installed webkitgtk and its dependencies from SBo, and the luakit and dwb browsers and their dependencies. However, both browsers perform very slowly. Sometimes they'll take upwards of 30 seconds to load a webpage that doesn't have any significant javascript. Using the same browsers (same versions, same config files) on Gentoo, they're quite fast, especially dwb. I'm not getting any error messages when I launch these browsers from the console. Firefox (v. 24, shipped with the distro) and other network applications seem to run at normal speed.

Can anyone suggest either how to speed things up, or how to diagnose the problem?

webkitgtk took a very long time to build, even with the Core i7 processor and 6GB of RAM, but it did build successfully. I used the GTK2 version and haven't tried the GTK3 version; would that make a difference?

Webkitgtk 2.x should be built against GTK+3.x for best results. Have you also resolved all the dependencies? Here's the known up to date list for webkitgtk-2.2.3

Gperf-3.0.4
gst-plugins-base-1.2.1
GTK+-3.10.6
ICU-52.1
libsecret-0.16
libsoup-2.44.2
libwebp-0.3.1
MesaLib-9.2.4
Ruby-2.0.0
SQLite-3.8.2
udev-extras (GUdev)*
Which-2.20
enchant-1.6.0
GeoClue-0.12.0
gobject-introspection-1.38.0
GTK-Doc-1.19 (optional)
MathML-2.0 (optional)

(*) I'm not certain if Slackware provides udev-extras gudev package.

For webkigtk-1.x (version 1.10.2 or better) should be built against the following:

Gperf-3.0.4
gst-plugins-base-0.10.36
GTK+-2.24.22
ICU-52.1
libsoup-2.44.2
MesaLib-9.2.4
Ruby-2.0.0
SQLite-3.8.2
Which-2.20
enchant-1.6.0
GeoClue-0.12.0
cURL-7.33.0
gobject-introspection-1.38.0
GTK-Doc-1.19 (optional)
MathML-2.0 (optional)

Plus to speed up the build time you can also use make -j# flags and replace the # sign with the number of cores per CPU you have such as for example make -j6 if you have a CPU with 6-cores.

The Slackbuild for webkitgtk explicitly builds the software with -j1, which explains the long build times. This is usually only done when the build fails with a higher number of threads.

just FYI I just tried building them (and the dependencies of both from SBo) and everything went fine: they look also very fast here.

Hmm, maybe I missed a dependency somewhere. I'll double-check everything. I know I didn't explicitly install everything from ReaperX7's list because not all of those are listed on SBo as dependencies---some of them are included in stock Slackware 14.1, but it's possible not everything is accounted for.

That list comes from BLFS, not SBo. Yes, Slackware does have many of those by default so they might not get a full listing, but there are several libraries that can aid and assist with certain functionality with a project provided they are installed. The BLFS list might be more comprehensive of a list as it lists Required, Recommended, and Optional packages you might want.

There are only a handful of projects I know of or have come across that refuse to accept anything other than -j1 with makeopts. Usually however, my build environment has -j2 always set to reduce the overhead of those compiles. Unless projects have specifically said -j2 or higher will fail, and -j1 must be used, I always go multi-core.

Compiling with -j2 (or greater) wouldn't have any effect on the speed of the browser once it's compiled, would it? I notice that the ebuild file for Gentoo's version of webkitgtk also explicitly specifies "make -j1", with a comment to the effect that multi-thread compiling sometimes fails.

no, it shouldn't.

The -j flag is a parameter of the make command, that tells make how many threads/processes to use to compile the software. It has no effect at all on the compiled software itself.

I recompiled webkitgtk against GTK3, using the same config as my Gentoo build of the same package. The browsers are still ridiculously slow on Slackware. 2.5 hours of compiling wasted.

The only dependency from ReaperX7's list that I'm not sure about is udev-extras/GUdev, but I can't find a script for it anywhere so it might be included in stock Slackware under a different name.

I will build and test dwb on my machine, if it runs fast I will upload the packages to my server, so that you can download and test them.

EDIT: OK, done that, and as I expected dwb is as fast as it could be on my machine. You can download my packages for it here to give it a try: http://slackeee.de/slackware/unofficial/dwb/

GUdev is not part of Slackware due to the fact Slackware uses the Classic-udev-standalone package, and not the systemd-udev-extracted package. I doubt it was part of the original udev also, but you probably could take a look at the Slackware udev source and find out.

Webkitgtk browsers often are not as fast as browsers possibly built from xulrunner like FireFox and SeaMonkey. However, any software could be dependent on your system as well specification-wise as to performance. However, this doesn't mean they aren't working correctly.

In my Gentoo installation on the same hardware, DWB is very fast.

I appreciate your taking the time to do this! Unfortunately, dwb is still quite slow on my Slackware.

Have you tried to run it from a terminal to see if there are any error messages?
If the same packages are running fast on my machine, but slow on yours I would think that not the packages, but the underlying system is at fault.