Package: shared-mime-info Version: 2.0-1 Severity: important Tags: upstream X-Debbugs-Cc: rossboy...@stanfordalumni.org
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Steps to Reproduce ================== 1. btrfs on top of encrypted partition on a spinning disk. btrfs subvolumes in use. 2. sources.list.d includes entry for Visual Studio code (deb [arch=amd64 signed-by=/usr/share/keyrings/microsoft-archive-keyring.gpg] https://packages.microsoft.com/repos/vscode stable main). 3. aptitude shows an update to code is available. 4. apply update and wait, as much as 45 minutes. Most of the time update-mime- database is consuming 50-90% of one CPU. This happens every time, even for the most minor update. I often am recording TV shows to the disk at the same time, but this morning I was not and it took 30 minutes. Other times it has been 40-45 minutes. Comments ======== I have opened a bug against vscode upstream (https://github.com/microsoft/vscode/issues/163690), and it seems likely their settings are not optimal. In particular, their postinst script invokes update- mime-database without the -n option. I do not usually experience such long delays when installing/upgrading other packages. I believe -n causes update-mime-database to skip scanning entirely if nothing seems new--the man page is a bit unclear. So perhaps that one fix would take care of most of my problems. However, when update-mime-database does a real run, it seems to me it should be much faster. This appears to be a long-standing problem: https://bugs.freedesktop.org/show_bug.cgi?id=70366 (also https://bugs.gentoo.org/487504, https://bugs.archlinux.org/task/66687, https://bugs.launchpad.net/ubuntu/+source/shared-mime-info/+bug/1816674). Some of the bugs have been closed, but I think in all cases that was because a facility to disable fsync() via an environment variable was added and the build or package installation system was modified to use it. In contrast, the performance I'm seeing strongly suggests it remains enabled on Debian. I spent some time trying to figure out how set the PKGSYSTEM_ENABLE_FSYNC environment variable so that it would be applied whenever update-mime-database ran. The answer is not obvious to me. The man page mentions no configuration files, and a quick look at main() in the source doesn't seem to show any being read in. main() does check the environment variable. I also looked for ways to set the variable in dpkg or apt, but didn't find anything (probably there is a way). Desired Solutions ================= In increasing order of difficulty/impact: 1. Document the PKGSYSTEM_ENABLE_FSYNC environment variable in the man page. 2. Describe how the user can disable the fsync during upgrades, bearing in mind that the invocation of update-mime-database is indirect. 3. Turn fsync off for update-mime-database as a default. I completely agree with Chantziaras's argument (https://bugs.freedesktop.org/show_bug.cgi?id=70366#c10) that using fsync on a database that can easily be rebuilt if things go wrong is unjustified. And, as noted above, disabling the fsync has been the common response across the various forms of packaging and build systems. Coda ==== The extremely poor performance I'm seeing is likely the result of failings in both the code packaging--not an official Debian package--and some weaknesses in btrfs. But problems with fsync in update-mime-database are widely reported, and it would be good if Debian could do something to mitigate them. - -- System Information: Debian Release: 11.5 APT prefers stable-security APT policy: (500, 'stable-security'), (500, 'stable') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 5.10.0-19-amd64 (SMP w/8 CPU threads) Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set Shell: /bin/sh linked to /usr/bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled Versions of packages shared-mime-info depends on: ii libc6 2.31-13+deb11u4 ii libglib2.0-0 2.66.8-1 ii libxml2 2.9.10+dfsg-6.7+deb11u3 shared-mime-info recommends no packages. shared-mime-info suggests no packages. -----BEGIN PGP SIGNATURE----- iQFSBAEBCgA8FiEEreS674/HIyV9gBfdnAYPmOsbK2AFAmNtjPgeHHJvc3Nib3ls YW5Ac3RhbmZvcmRhbHVtbmkub3JnAAoJEJwGD5jrGytg37cIAJWqFm4HkUfw6AX+ vlAR5gsFIxZ3qeCJFHqTx4GIXWvXNIIHx9SpKTbQmDFw9QbqRp9se/zTVfFshUde v5hxyQ+1AF8iYH+OkbLKsDGNnyoDW15DzKY35ZTbnzLBNtKQ7E31fBah9icr6Asx Unj3aXSjxWxqH6alGOVu2Sr7jA5QH5tsUU99uSTYreUGQuXUqk0UnNv4DdCIZzLi o47U9gDGXLSL2tSWK3TTaFeUv97w/eaGzd0/FnUQGWnvfWcIKCZWyNOsFDkhFhgw Dk3UPTkgFesAM8fAF2zUW3nMbCuuoaVmtYizJdizO9XPB83L9KN18RHO3Lt6AAmO 64PabuU= =qsw3 -----END PGP SIGNATURE-----
