Re: [Qemu-devel] [PATCH 3/4] Switch from array based resource allocation to list

[Alexey Korolev]

[...]
>> [Patch 5]
>> Track-alignment-explicitly
>> Almost the same as the previous, just changed priority from r->align to 
>> r->sum when setting start address of root regions.
>>
>> I guess there are more chances to fit memory regions if we try place regions 
>> with higher r->sum like it was before.
>> Consider default config
>> #define BUILD_PCIMEM_START       0xe0000000
>> #define BUILD_PCIMEM_END          0xfec00000
>>
>> Image we have 1 pref. mem. region of 128MB. And many small memory regions 
>> which take rest of available 492MB - 128MB
>> If we have alignment priority.
>> PCI pref memory region will start from F000 0000
>> and
>> PCI memoryregion will start from 0xe0000000
>> and do not fit.
>
>The section with the lowest alignment would get allocated first and be
>at a higher address.  So, in your example, the regular memory region
>would be assigned 0xe8000000 and then pref mem would be assigned
>0xe0000000.
>
>Your example is why alignment should be used instead of size.  If size
>is used, then what you cite above occurs (pref mem has the lower size
>and is thus allocated first at the higher address).

Ahh the lowest alignment! In other words if we go from PCIMEM_START to 
PCIMEM_END we first
assign address range for the region with the largest PCI resource size (highest 
alignment). 
I see. I will put it back then.

....
>On patch 10, it would be preferable to separate the dynamic
>calculation of sum/alignment changes from the 64bit support.
>Otherwise, the core algorithm of patch 10 looks okay.  Though it seems
>like the code is recalculating sum/alignment more than needed, and I
>think the list manipulation in pci_region_migrate_64bit_entries could
>be streamlined.
Right, sum/alignment recalculation is important for migration. Will split it 
and submit new series.

Thanks,
Alexey