On Wed, Nov 09, 2016 at 02:50:43PM +0100, Michael Biebl wrote: > Hi, > > currently, when trying to opan a Fedora journal file from Debian/Ubuntu I get: > Journal file .../system.journal uses an unsupported feature, ignoring file. > > This is probably due to Debian not having lz4 support enabled (yet). > We currently only build with XZ compression. > > I wonder what other distros, besides Debian and Fedora, have chosen here. > Do you enable LZ4 or XZ compression? > > We have a bug report in Debian, which asks us to enable LZ4 > compression, because XZ is just too slow for coredumps [1]. > Since journal files and coredumps use the same compression, this would > mean, new journal files are written using LZ4. Which in turn means, > we'd basically have to support LZ4 forever. > Is this a concern that is shared by other distros / upstream?
LZ4 is not perfect (the compression is a tad low, no threading), but it's waaaay better than XZ for the purposes of systemd. In Fedora, "watchdog crashes" of journald when slow hardware is overloaded are the most commonly reported bug. Debian users are certainly affected by this too, and super-slow XZ compression exacerbates the issue. I'd encourage you to switch. In particular, you should enable LZ4 *decompression*, so that journal files produced on other systems are supported. Now supporting all decompression formats is encouraged, since we have only two. I don't think it'd be a big issue to disable XZ decompression in a distro a few years after switching to LZ4, but OTOH, the gains would be minimal. In Fedora, rpm links to liblzma, so effectively it is always installed. Zbyszek _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
