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Re: [Qemu-block] [2.4 PATCH v3 07/19] hbitmap: add hbitmap_merge

From: Max Reitz
Subject: Re: [Qemu-block] [2.4 PATCH v3 07/19] hbitmap: add hbitmap_merge
Date: Mon, 16 Mar 2015 16:55:38 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

On 2015-03-13 at 14:30, John Snow wrote:
We add a bitmap merge operation to assist in error cases
where we wish to combine two bitmaps together.

This is algorithmically O(bits) provided HBITMAP_LEVELS remains
constant. For a full bitmap on a 64bit machine:
sum(bits/64^k, k, 0, HBITMAP_LEVELS) ~= 1.01587 * bits

We may be able to improve running speed for particularly sparse
bitmaps by using iterators, but the running time for dense maps
will be worse.

We present the simpler solution first, and we can refine it later
if needed.

Signed-off-by: John Snow <address@hidden>
  include/qemu/hbitmap.h | 11 +++++++++++
  util/hbitmap.c         | 29 +++++++++++++++++++++++++++++
  2 files changed, 40 insertions(+)

Reviewed-by: Max Reitz <address@hidden>

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