** Description changed:
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.
+ 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
+ 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.
** Changed in: linux (Ubuntu Disco)
Status: Incomplete => Confirmed
** Changed in: linux (Ubuntu Cosmic)
Status: Incomplete => Confirmed
** Changed in: linux (Ubuntu Bionic)
Status: Incomplete => Confirmed
** Changed in: linux (Ubuntu Xenial)
Status: Incomplete => Confirmed
** Changed in: linux (Ubuntu Ee-series)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1824864
Title:
CONFIG_LOG_BUF_SHIFT set to 14 is too low on arm64
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