Linux 6.4

While we wait to see what Red Hat's new source code policy does to RHEL rebuilds like RockyLinux and Alma Linux downstream, Linux 6.4 came out this week. Aside from things like new hardware support, filesystem improvements (such as a small performance win for ext4) and more Rust code, and the removal of the old SLOB memory allocator, there's not a lot here on the Power ISA side this time around except for the removal of various older evaluation boards. Expect to see it in Fedora and more leading edge distributions shortly.

Firefox 114 on POWER

Firefox 114 is released. The biggest update in my humble opinion is that (assuming you're running Linux) you can now use FIDO2/WebAuthn authenticators over USB, and virtually all of them should "just work" with OpenPOWER hardware. I'm going to try this out and report back but cursorily looking at the source code I don't see any reason why it would be incompatible. If you bought your POWER9 for security purposes, or even if you just like being secure-adjacent, here's another advance to take advantage of. A more nebulous new feature in 114 is support for WebTransport, which adds low-latency datagram-grade server communication and should facilitate more interactive applications but will probably just be another way for sites to spy on you. Oh well! This initial cut requires HTTP/3 but HTTP/2 support is coming.

Fx114 will not build out of the box. First, as usual you'll need to deal with bug 1775202, either by putting --disable-webrtc in your .mozconfig if you don't need WebRTC, or patching third_party/libwebrtc/moz.build. Unfortunately the patches in that bug no longer serve, so here's the diff on mine, which builds the browser I'm typing in now.

Second, there's a regression in the profiler which breaks linking, filed as bug 1838584 and also present in Firefox 115 currently, apparently a regression from bug 1824465. The provided patch in the bug fixes the issue but unless this lands on beta you'll need this patch again for Fx115.

The browser otherwise builds and works with the PGO-LTO patch for Firefox 110 and the .mozconfigs from Firefox 105.

Also, I might take the opportunity to make a performance reminder: if you have a lot of threads available (on this dual-8 Talos II, I have 64 because SMT-4), you can modestly increase dom.ipc.processCount and get better throughput. I use 12. Increase this pref with care, because you'll need memory to match (I have 64GB), and other kinds of content processes may not count against that cap: with that setting, ps auxww | grep firefox | grep -c contentproc currently gives me a count of 31. Be sure to uncheck "Use recommended performance settings" in Firefox's preferences before changing this count in about:config. about:processes can give you a better idea of what content processes exist and what they're doing.

SDL2 VMX bugfix

Another hat tip to Jeremy Rand, who got a fix landed for issues with VMX endianness with blitting inside the SDL library. We all care about SDL, since many games rely on it (and quite a few other things), and the issue was a real performance problem with ppc64le as at least some distros dealt with the issue by disabling it on little-endian (big-endian Power is unaffected). The patch is also faster because it moves the vector permute out of the loop, which is also the correct fix for the bug. The issue goes back all the way to the original SDL; the patch has landed on the legacy SDL 1.2.x as well as the next release of SDL 2.x, expected to be 2.28.

Jeremy added, "My patch was reviewed promptly, and it's obvious that SDL actually cares about properly supporting diverse arches, even if they don't personally use them." Amen to that.