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

[Koichiro Den]

On Thu, Nov 07, 2024 at 09:35:59AM +0800, Guoqing Jiang wrote:
> 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

Ugh, thank you for pointing it out.
I'll send v2, including Agathe's feedback as well. Thanks to both of you
for reviewing.

> 
> 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(-)
> > 
>