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Re: [Qemu-block] [PATCH v4 07/20] hbitmap: add hbitmap_merge
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH v4 07/20] hbitmap: add hbitmap_merge |
Date: |
Thu, 2 Apr 2015 13:19:41 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Fri, Mar 20, 2015 at 03:16:50PM -0400, 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>
> Reviewed-by: Max Reitz <address@hidden>
> ---
> include/qemu/hbitmap.h | 11 +++++++++++
> util/hbitmap.c | 29 +++++++++++++++++++++++++++++
> 2 files changed, 40 insertions(+)
Reviewed-by: Stefan Hajnoczi <address@hidden>
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Stefan Hajnoczi <=