Re: performance tuning, problem with paravirtualized clock

[Anthony Liguori <anthony@codemonkey.ws>]

Nikola Ciprich wrote:
> Anthony Liguori wrote:
>> You won't see a gain with tmpfs.  Make sure you reserve huge pages 
>> first.  For a 1GB guest, you'll need something like:
>>
>> echo 540 > /proc/sys/vm/nr_hugepages
>>
>> When you create a VM, you need a bit more memory than 1GB for 
>> per-guest overhead.  That's why I reserve 540 instead of 512.  You 
>> can probably get away with 530 really.
>>
>> Check that it succeeded by cat'ing /proc/meminfo.
>>
> Well, I tried various values now, and booting fails immediately:
> Decompressing Linux...

It's very likely that you won't be able to allocate enough pages to run 
a guest if your system has been running sufficient long and memory is 
highly fragmented.

If you cat /proc/meminfo and HugePages_Free is much less than 540, 
you're not going to be able to create a 1GB guest.  Unfortunately, you 
won't get a failure until the guest tries to use memory.

The only solution is to reboot and reserve huge pages early before they 
get fragmented.

Regards,

Anthony Liguori

> invalid compressed format (err=1)
>
> -- System halted
>
>
> weird...
> anyways I'll also give fresh kvm-65 a try now :)
>


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