Re: xl dmesg buffer too small for Xen 4.18?

[Chuck Zmudzinski <brchuckz@xxxxxxxxxxxx>]

On 9/18/2023 9:00 AM, Chuck Zmudzinski wrote:
> Hello,
> 
> I tested Xen 4.18~rc0 on Alma Linux 9 and my first tests indicate it works 
> fine for starting the guests I manage but I notice that immediately after 
> boot and with only dom0 running on the system, I get:
> 
> [user@Malmalinux ~]$ sudo xl dmesg
> 00bee72000-00000bee72fff type=7 attr=000000000000000f
> (XEN)  00000bee73000-00000bef49fff type=4 attr=000000000000000f
> (XEN)  00000bef4a000-00000bef4bfff type=7 attr=000000000000000f
> (XEN)  00000bef4c000-00000befbafff type=4 attr=000000000000000f
> (XEN)  00000befbb000-00000befbbfff type=7 attr=000000000000000f
> ...
> 
> I have noticed the buffer fills up quickly on earlier Xen versions, but never 
> have I seen it fill up during boot and with only dom0 running.
> 
> Can increasing the buffer fix this? How would one do that?
> 
> Thanks
> 

I see the setting is the command line option conring_size:

https://xenbits.xen.org/docs/unstable/misc/xen-command-line.html#conring_size

The default is 16k, I tried 48k and that was big enough to capture all the 
messages at boot for 4.18 rc0. This is probably not an issue if the release 
candidate is being more verbose than the actual release will be. But if the 
release is still this verbose, maybe the default of 16k should be increased.