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Date: Tue, 12 Mar 2013 10:04:42 -0600
From: Eric Blake <eblake@redhat.com>
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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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To: Peter Lieven <pl@dlhnet.de>
Cc: Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Orit Wasserman <owasserm@redhat.com>

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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.
>=20
> compared to loop unrolling this adds another 50% performance
> benefit for skipping large areas of zeroes.
>=20
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  util/bitops.c |   23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)

> +        if (((uintptr_t) p) % sizeof(VECTYPE) =3D=3D 0
> +              && size >=3D BITS_PER_BYTE*8*sizeof(VECTYPE)) {

Spaces around binary operators.  CHAR_BITS instead of magic 8.

> +          unsigned long tmp2 =3D
> +              buffer_find_nonzero_offset(p, ((size/BITS_PER_BYTE) &
> ~(8*sizeof(VECTYPE)-1)));

Spaces around binary operators.

--=20
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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