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Re: [Qemu-devel] [RFC][PATCH 7/9] bitops: use vector algorithm to optimi
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From: |
Eric Blake |
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Subject: |
Re: [Qemu-devel] [RFC][PATCH 7/9] bitops: use vector algorithm to optimize find_next_bit() |
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Date: |
Tue, 12 Mar 2013 10:04:42 -0600 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 |
On 03/12/2013 09:52 AM, Peter Lieven wrote:
> this patch adds the usage of buffer_find_nonzero_offset()
> to skip large areas of zeroes.
>
> compared to loop unrolling this adds another 50% performance
> benefit for skipping large areas of zeroes.
>
> Signed-off-by: Peter Lieven <address@hidden>
> ---
> util/bitops.c | 23 ++++++++++++++++++++---
> 1 file changed, 20 insertions(+), 3 deletions(-)
> + if (((uintptr_t) p) % sizeof(VECTYPE) == 0
> + && size >= BITS_PER_BYTE*8*sizeof(VECTYPE)) {
Spaces around binary operators. CHAR_BITS instead of magic 8.
> + unsigned long tmp2 =
> + buffer_find_nonzero_offset(p, ((size/BITS_PER_BYTE) &
> ~(8*sizeof(VECTYPE)-1)));
Spaces around binary operators.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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