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SubjectRe: [RFC PATCH 0/3] Weight-balanced binary tree + KVM growable memory slots using wbtree
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
>

--
error compiling committee.c: too many arguments to function



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