Re: [Qemu-devel] [PATCHv2 2/9] cutils: add a function to find non-zero content in a buffer

[Eric Blake <eblake@redhat.com>]

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On 03/19/2013 10:18 AM, Peter Lieven wrote:
> 
> Am 19.03.2013 um 16:54 schrieb Eric Blake <eblake@redhat.com>:
> 
>> On 03/15/2013 09:50 AM, Peter Lieven wrote:
>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>> ---
>>> include/qemu-common.h |    2 ++
>>> util/cutils.c         |   40 ++++++++++++++++++++++++++++++++++++++++
>>> 2 files changed, 42 insertions(+)
>>>
>>
>>>
>>> +#define BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR 8
>>
>> Good.
>>
>>> +    assert(len % (BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR 
>>> +        * sizeof(VECTYPE)) == 0);
>>
>> Good use of it.
> 
> A question I had is if these asserts make the code slower? In case of all
> the 4k pages in RAM migration this could be significant.

Yes, it probably does slow things down when asserts are enabled.  I'm
not sure whether it is better to keep the code forcefully robust, or to
rely on auditing all callers for properly obeying assumptions.  Maybe
you should wait for an opinion from one of the maintainers.

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


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