Re: [Qemu-devel] [PATCH qemu] sysemu: support up to 1024 vCPUs

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 19/10/16 23:23, Igor Mammedov wrote:
> On Wed, 19 Oct 2016 10:39:12 +1100
> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
> 
>> On 18/10/16 22:00, Igor Mammedov wrote:
>>> On Tue, 11 Oct 2016 09:19:10 +1100
>>> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
>>>   
>>>> Ping, anyone?  
>>> I have a similar patch
>>> http://patchwork.ozlabs.org/patch/681709/
>>> which bumps limit to 288 and does a little bit more
>>> so it wouldn't affect current users.  
>>
>> Why 288 (not oldlimit<<n)? :)
> That's how many vCPU we plan to support for target-i386.


So that patch from patchworks should actually be 3 patches -
- untie MAX_CPUMASK_BITS from maxcpus;
- increase MAX_CPUMASK_BITS to 1024 (till we get this thing totally dynamic);
- increase maxcpus for x86 to 288.

and on top of this I (or Greg) would repost pseries change to maxcpus=1024

Correct? Has your patch gone anywhere yet?



> 
> 
>> What does happen to the Greg's patch now?
> it could be amended to apply top of above patch,
> 
> where it would change not only MAX_CPUMASK_BITS but also
> maxcpus in ppc target since above patch unties maxcpus
> from MAX_CPUMASK_BITS for all targets.
> 
> So followup increases of MAX_CPUMASK_BITS won't affect
> other targets.
> 
>>
>>
>>>
>>> After that's merged, I plan to get rid of this limit and
>>> make that part of numa parsing code dynamic so that it
>>> wouldn't impose such limit/any limits on target code.
>>>   
>>>>
>>>>
>>>> On 04/10/16 11:33, Alexey Kardashevskiy wrote:  
>>>>> From: Greg Kurz <gkurz@linux.vnet.ibm.com>
>>>>>
>>>>> Some systems can already provide more than 255 hardware threads.
>>>>>
>>>>> Bumping the QEMU limit to 1024 seems reasonable:
>>>>> - it has no visible overhead in top;
>>>>> - the limit itself has no effect on hot paths.
>>>>>
>>>>> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>> ---
>>>>>  include/sysemu/sysemu.h | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
>>>>> index ef2c50b..2ec0bd8 100644
>>>>> --- a/include/sysemu/sysemu.h
>>>>> +++ b/include/sysemu/sysemu.h
>>>>> @@ -173,7 +173,7 @@ extern int mem_prealloc;
>>>>>   *
>>>>>   * Note that cpu->get_arch_id() may be larger than MAX_CPUMASK_BITS.
>>>>>   */
>>>>> -#define MAX_CPUMASK_BITS 255
>>>>> +#define MAX_CPUMASK_BITS 1024
>>>>>  
>>>>>  #define MAX_OPTION_ROMS 16
>>>>>  typedef struct QEMUOptionRom {
>>>>>     
>>>>
>>>>  
>>>   
>>
>>
> 


-- 
Alexey