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 4/9] buffer_is_zero: use vector optimizations if possible
Date: Tue, 12 Mar 2013 10:09:35 -0600 [thread overview]
Message-ID: <513F533F.1010605@redhat.com> (raw)
In-Reply-To: <B3045697-71E3-4203-B575-44BC1F7E73AB@dlhnet.de>
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On 03/12/2013 10:03 AM, Peter Lieven wrote:
>>> + if (((uintptr_t) buf) % sizeof(VECTYPE) == 0
>>> + && len % 8*sizeof(VECTYPE) == 0) {
>>
>> Space around binary operators. Use CHAR_BITS instead of a magic number
>> 8.
> the 8 is not BITS_PER_BYTE or CHAR_BITS its the number of
> vectors in one loop in buffer_find_nonzero_offset(). I will add
> a constant for this to make it clearer.
Indeed, now I see it - 8 is the unroll factor. Well, all the more
evidence that a named constant makes the code easier to read, compared
to me mis-interpreting the magic number.
--
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 16:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 15:50 [Qemu-devel] [RFC][PATCH 4/9] buffer_is_zero: use vector optimizations if possible Peter Lieven
2013-03-12 16:01 ` Eric Blake
2013-03-12 16:03 ` Peter Lieven
2013-03-12 16:09 ` Eric Blake [this message]
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