On Wed, Aug 19, 2020 at 2:23 PM Dave Young <dyoung(a)redhat.com> wrote:
On 08/12/20 at 02:32pm, Lianbo Jiang wrote:
> Sometimes, debugging the kdump service failure becomes very challenging
> because there is no complete debugging information, which requires
> modification of the options or the scripts like kdumpctl, mkdumprd, etc
> to collect the information for troubleshooting.
> That means users have to wait for the next failure so that they can
> capture the additional information, which could waste valuable time.
> This patch series will add the debugging messages and save them to a
> file. It includes the following patches:
>  [PATCH 1/2] kdumpctl/mkdumprd: add 'set -x' to output debugging
> information to a file
>  [PATCH 2/2] kdumpctl: add the '-d' option to enable the kexec loading
> debugging messages
 should be good, but for , I'm not sure if this can make kdump
service startup even slower. Have you compared the performance
with/without the change?
I agree with Dave's comment above. I am particularly worried about the
arm64 systems which take a lot of time when MMU is turned off during
kdump relocation (for e.g. the thunderx2 systems).
I have a couple of suggestions:
- Let's keep a option to enable or disable this logging - not every
user would like to enable this 'additional' debug information (log
file creation) by default. So how about providing and additional
parameter in the kdump configuraiton file(s) to see if this has been
enabled explicitly by user. kdumpctl can accordingly enable the '-x'
- Also how about doing a simple 'time' comparision with and without
the [PATCH 1/2].
BTW, "set -x" usually means too much noise, we may need to
loglevel, export fine grained logs if possible by default, the export the whole
"set -x" logs when the logleve is set as max.
Another question is there is an option in dracut below:
output debug information of the build process
increase verbosity level (default is info(4))
For /sbin/mkdumprd debuggin, should we just use the dracut option for
dracut debug info?
Maybe you have tried to use logger, do you have other reason to drop the
usage? With this patches applied, not sure if the original visible logs
in systemd journal will disappear or not.
> Changes since v1:
>  Set default log path to '/var/log/kdump' instead of
>  Add a timestamp to the debug log messages
>  Print a message to differentiate between the kdumpctl and mkdumprd log
> Lianbo Jiang (2):
> kdumpctl/mkdumprd: add 'set -x' to output debugging information to a
> kdumpctl: add the '-d' option to enable the kexec loading debugging
> kdumpctl | 12 +++++++++++-
> mkdumprd | 10 ++++++++++
> 2 files changed, 21 insertions(+), 1 deletion(-)
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