Hi community
Does ID3D12CommandQueue::ExecuteCommandLists() guarantee command lists will be executed in order?
For example:
ID3D12CommandList* ppCommandLists[] = { cmdList0, cmdList1, cmdList2, cmdList3 };
m_commandQueue->ExecuteCommandLists(_countof(ppCommandLists), ppCommandLists);
cmdListN will be executed before cmdListM where N < M? MSDN documentation does not mention anything about that, so I do not know if that is undefined / GPU/driver dependant / etc.
All of the work submitted in a single call to ExecuteCommandLists is guaranteed to complete before the next batch of work submitted in a subsequent call, but within a single "execution group," the driver may be able to re-order commands, or maintain pipelining, as if it was a single command list.
All of the work submitted in a single call to ExecuteCommandLists is guaranteed to complete before the next batch of work submitted in a subsequent call, but within a single "execution group," the driver may be able to re-order commands, or maintain pipelining, as if it was a single command list.
Does this mean that submitting command lists with dependencies between each other, in a single batch, is not reliable?
IIRC to ensure coherency between draw calls within a single executecommandlists batch you use resource barriers. They will flush caches and prevent pipelining and whatever is necessary to ensure coherency.
edit - here watch this:
I just did a quick test. I executed 4 command lists in a single ID3D12CommandQueue::ExecuteCommandLists() and it worked properly over multiple frames.
cmdList1 = CD3DX12_RESOURCE_BARRIER::Transition(resource, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE, D3D12_RESOURCE_STATE_RENDER_TARGET),
cmdList2 = CD3DX12_RESOURCE_BARRIER::Transition(resource, D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE),
cmdList3 = CD3DX12_RESOURCE_BARRIER::Transition(resource, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE, D3D12_RESOURCE_STATE_RENDER_TARGET),
cmdList4 = CD3DX12_RESOURCE_BARRIER::Transition(resource, D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE),
ID3D12CommandList* cmdLists = { cmdList1, cmdList2, cmdList3, cmdList4 };
cmdQueue.ExecuteCommandLists(__countof(cmdLists), cmdLists);
