CMT: [SRU][AWS][F][PATCH 0/1] Set CONFIG_LOG_BUF_SHIFT=18 on all 64bit arches

[Guoqing Jiang]

Hi,

On 11/6/24 01:33, Koichiro Den wrote:
> BugLink: https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/2085493

For BugLink, pls use  this one.

https://bugs.launchpad.net/bugs/2085493

Thanks,
Guoqing

> SRU Justification:
>
> [Impact]
>
> CONFIG_LOG_BUF_SHIFT has been kept at 14 on arm64 instances. The small
> log_buf has led to sporadic test failures (see LP#2085493). Furthermore,
> since it can easily fill up before systemd-journald starts, some boot
> kernel log messages may be lost. Align the settings with master kernel
> for simplicity's sake, including other architectures.
>
> [Fix]
>
> Set CONFIG_LOG_BUF_SHIFT=18, which is sufficient in normal
> circumstances.
>
> [Test Plan]
>
> Boot testing suffices.
> I have tested with log_buf_len=256K on b:linux-aws-5.4 and confirmed that the
> sporadic failures observed in LP#2085493 disappeared.
>
> [Where problems could occur]
>
> Raising the size of the log_buf will increase kernel memory usage
> which cannot be reclaimed. On arm64 instance types, the size will
> increase from 16 KB to 256 KB. Users who want to keep it at 16 KB
> might need to explicitly set log_buf_len= kernel parameter.
>
>
> Koichiro Den (1):
>    UBUNTU: [Config] aws: CONFIG_LOG_BUF_SHIFT=18 on all 64bit arches
>
>   debian.aws/config/annotations | 1 -
>   1 file changed, 1 deletion(-)
>