$ cat /boot/config-5.0.0-16-generic | grep LOG_BUF CONFIG_LOG_BUF_SHIFT=18 CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=13
$ uname -a Linux doerfel 5.0.0-16-generic #17-Ubuntu SMP Wed May 15 10:54:19 UTC 2019 aarch64 aarch64 aarch64 GNU/Linux And journal shows complete kernel boot messages, thus this all now good on disco. ** Tags removed: verification-needed-disco ** Tags added: verification-done-disco ** No longer affects: systemd (Ubuntu Xenial) ** No longer affects: systemd (Ubuntu Bionic) ** No longer affects: systemd (Ubuntu Cosmic) ** No longer affects: systemd (Ubuntu Disco) ** No longer affects: systemd (Ubuntu Eoan) ** No longer affects: systemd (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1824864 Title: CONFIG_LOG_BUF_SHIFT set to 14 is too low on arm64 Status in linux package in Ubuntu: Confirmed Status in linux source package in Xenial: Confirmed Status in linux source package in Bionic: Confirmed Status in linux source package in Cosmic: Confirmed Status in linux source package in Disco: Fix Committed Status in linux source package in Eoan: Confirmed Bug description: [Impact] * Too small dmsg kernel buf ring size leads to loosing/missing early boot kernel messages which happen before journald starts slurping them up and storing them on disc. This results in messages similar to this one on boot "missed NN kernel messages on boot". This is especially pronounced on arm64 as the default setting there is way lower than any other 32bit or 64bit architecture we ship. Also amd64 appears to have the highest setting of 18 among all architectures we ship. The best course of action to bump all 64bit arches to 18, and keep all 32bit arches at the current & upstream default of 17. [Test Case] * $ cat /boot/config-`uname -r` | grep CONFIG_LOG_BUF_SHIFT on 64bit arches result should be: CONFIG_LOG_BUF_SHIFT=18 on 32bit arches result should be: CONFIG_LOG_BUF_SHIFT=17 * run systemd adt test, the boot-and-services test case should not fail journald tests with "missed kernel messages" visible in the error logs. [Regression Potential] * Increasing the size of the log_buf, will increase kernel memory usage which cannot be reclaimed. It will now become 256kb on arm64, ppc64el, s390x instead of 8kB/128kb/128kb respectively. 32bit arches remain unchanged at 128kb. [Other Info] * Original bug report CONFIG_LOG_BUF_SHIFT policy<{ 'amd64' : '18', 'arm64' : '14', 'armhf' : '17', 'i386' : '17', 'ppc64el': '17', 's390x' : '17'}> Please set CONFIG_LOG_BUF_SHIFT to at least 17 on arm64. Potentially bump all 64-bit arches to 18 (or higher!) as was done on amd64, meaning set 18 on arm64 s390x ppc64el. I have a systemd autopkgtest test that asserts that we see Linux kernel command line in the dmesg (journalctl -k -b). And it is consistently failing on arm64 scalingstack KVM EFI machines with messages of "missing 81 kernel messages". config LOG_BUF_SHIFT int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" range 12 25 default 17 depends on PRINTK help Select the minimal kernel log buffer size as a power of 2. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config parameter, see below. Any higher size also might be forced by "log_buf_len" boot parameter. Examples: 17 => 128 KB 16 => 64 KB 15 => 32 KB 14 => 16 KB 13 => 8 KB 12 => 4 KB 14 sounds like redictiously low for arm64. given that 17 is default across 32-bit arches, and 18 is default on amd64. On a related note, we have CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT policy<{'amd64': '13', 'arm64': '13', 'armhf': '13', 'i386': '13', 'ppc64el': '13', 's390x': '13'}> I'm not sure if we want to bump these up to LOG_BUF_SHIFT size or not. Please backport this to xenial and up. === systemd === systemd, boot-and-services test case can bump the ring buffer before running the tests. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1824864/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
