On 02/22/2011 08:54 PM, Alex Williamson wrote:
This series introduces a new weight-balanced binary tree (wbtree) for general use. It's largely leveraged from the rbtree, copying it's rotate functions, while introducing different rebalance and erase functions. This tree is particularly useful for managing memory ranges, where it's desirable to have the most likely targets (the largest ranges) at the top of each subtree. Patches 2& 3 go on to convert the KVM memory slots to a growable array and make use of wbtree for efficient managment. Trying to exercise the worst case for this data structure, I ran netperf TCP_RR on an emulated rtl8139 NIC connected directly to the host via a tap. Both qemu-kvm and the netserver on the host were pinned to optimal CPUs with taskset. This series resulted in a 3% improvement for this test.
In this case, I think most of the faults (at least after the guest was warmed up) missed the tree completely. In this case a weight balanced tree is hardly optimal (it is optimized for hits), so I think you'll see a bigger gain from the mmio fault optimization. You'll probably see most of the gain running mmu intensive tests with ept=0.
Note that part of why this series is RFC is that the print_tree function in the last patch is debug code that generates output for dot. You can copy the output to a file and run: dot -Tpdf foo.dot> foo.pdf to generate a nice diagram of the tree currently in use. I'll follow-up with a few examples. Thanks, Alex
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