Re: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary hugepage zero-filling

["Xie, Huawei" <huawei.xie@intel.com>]

On 11/18/2015 6:45 PM, Wang, Zhihong wrote:
>> -----Original Message-----
>> From: Mcnamara, John
>> Sent: Wednesday, November 18, 2015 6:40 PM
>> To: Wang, Zhihong <zhihong.wang@intel.com>; dev@dpdk.org
>> Subject: RE: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary
>> hugepage zero-filling
>>
>>
>>
>>> -----Original Message-----
>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zhihong Wang
>>> Sent: Wednesday, November 18, 2015 3:27 AM
>>> To: dev@dpdk.org
>>> Subject: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary
>>> hugepage zero-filling
>>>
>>> The kernel fills new allocated (huge) pages with zeros.
>>> DPDK just has to touch the pages to trigger the allocation.
I think we shouldn't reply on the assumption that kernel has zeroed the
memory. Kernel zeroes the memory mostly to avoid information leakage.It
could also achieve this by setting each bit to 1.
What we indeed need to check is later DPDK initialization code doesn't
assume the memory has been zeroed. Otherwise zero only that part of the
memory. Does this makes sense?

>>> ...
>>>  		if (orig) {
>>>  			hugepg_tbl[i].orig_va = virtaddr;
>>> -			memset(virtaddr, 0, hugepage_sz);
>>> +			memset(virtaddr, 0, 8);
>>>  		}
>> Probably worth adding a one or two line comment here to avoid someone
>> thinking that it is a bug at some later stage. The text in the commit message
>> above is suitable.
>>
> Good suggestion! Will add it :)
>
>> John.
>> --
>