From: Eric Blake <eblake@redhat.com>
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>
Subject: Re: [Qemu-devel] [RFC][PATCH 7/9] bitops: use vector algorithm to optimize find_next_bit()
Date: Tue, 12 Mar 2013 10:04:42 -0600 [thread overview]
Message-ID: <513F521A.9080700@redhat.com> (raw)
In-Reply-To: <513F4F4E.1060009@dlhnet.de>
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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.
>
> compared to loop unrolling this adds another 50% performance
> benefit for skipping large areas of zeroes.
>
> 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) == 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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prev parent reply other threads:[~2013-03-12 16:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 15:52 [Qemu-devel] [RFC][PATCH 7/9] bitops: use vector algorithm to optimize find_next_bit() Peter Lieven
2013-03-12 16:04 ` Eric Blake [this message]
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