Re: [Patch v2] docs: Correct docs for extra_guest_irqs command line option

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 31/07/13 14:39, Ian Campbell wrote:
> On Wed, 2013-07-31 at 14:35 +0100, Andrew Cooper wrote:
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Ian Campbell <Ian.Campbell@citrix.com>
>> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
>>
>> ---
>> Changes for v2:
>>  * Spelling
>>  * Clarification about the effects of optional parameters
>> ---
>>  docs/misc/xen-command-line.markdown |   10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
>> index 708ffc2..775a018 100644
>> --- a/docs/misc/xen-command-line.markdown
>> +++ b/docs/misc/xen-command-line.markdown
>> @@ -485,9 +485,15 @@ disable it (edid=no). This option should not normally be required
>>  except for debugging purposes.
>>  
>>  ### extra\_guest\_irqs
>> -> `= <number>`
>> +> `= [<domU number>][,<dom0 number>]`
>>  
>> -Increase the number of PIRQs available for the guest. The default is 32. 
>> +> Default: `32,256`
>> +
>> +Change the number of PIRQs available for guests.  The optional first number is
>> +common for all domUs, while the optional second number (preceded by a comma)
>> +is for dom0.  The numbers for domains are only changed if the option is
>> +specified.  For example to change dom0 without changing domU, use
>> +`extra_guest_irqs=,512`
> So the effect of extra_guest_irqs=512 is to change only domU and not
> dom0?

Correct.  There used to be no split between dom0 and domU, but with
larger platforms and "interrupt-per-vcpu" becoming common with 10G
network cards, 32 just didn't cut it for dom0.

I noticed this documentation bug as we now have a server where 256 is
insufficient for dom0.

>
> Perhaps:
>
> "The numbers for domains are only changed if the option is specified."
> => "Changing the setting for domU has no impact on dom0 and vice versa."
>
> Ian.
>
>

I would hope that it in implicit that domU != dom0, but I guess being
clearer is better.  v3 on its way.

~Andrew