Re: xl dmesg buffer too small for Xen 4.18?

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.09.2023 20:49, Julien Grall wrote:
> On 18/09/2023 19:17, Chuck Zmudzinski wrote:
>> On 9/18/2023 9:00 AM, Chuck Zmudzinski wrote:
>>> 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.

Just to mention it: Log-level defaults are different for debug and release 
builds,
which means release builds are typically less verbose.

Jan