RE: 16 vcpus, 200GB of memory boots!!!

Jes Sorensen wrote:
> Zhang, Xiantao wrote:
>>> I have located a 512 cpu / 1 TB system in-house that I might get my
>>> hands on at some point to run tests on, but I need to work on the
>>> qemu startup times first. It took well over 20 minutes for qemu to
>>> get going before anything really happened.
>> Hi, Jes
>>     How long does it cost from efi shell to Linux's login interface
>> ? Currently, we allocates so large memory for guests,  kvm has to
>> pin the corresponding pages in p2m table other than allocate them
>> on-demand, so it may cost long time to allocate every page from
>> kernel, and fill them into p2m table. Once we support host-swapping
>> later, the issue should disappear. But anyway, it can't lead into
>> any performance issue after bootup.  To support larger memory than
>> 384G, we may allocate contiguous huge pages, such as 16M, 256M pages
>> for guest, if so, it may save many p2m entries because one entry can
>> stand for 16M or 256M, so larger memory gets supported finally.
>> Xiantao         
> 
> Hi Xiantao,
> 
>  From EFI to Linux's login wasn't bad, I didn't notice it being much
> slower than on real hardware. The big issue was from QEMU until EFI,
> it took probably 20 minutes or more before I started getting any of
> the debug information from the firmware image on the console :-( I
> think what is happening right now is something in qemu being really
> slow. 
> 
> It's end of day here for me, but I hope to look at it tomorrow.


Hi, Jes
	I found the reason why qemu only supports 16 vcpus.  In
libkvm/kvm-common.h, the MAX_CPUS is defined as 16 for ia64 side.  We
should increase this value to 64 or big value you like.  Please have a
try on your mainframe.  Thanks!
Xiantao