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

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 23 Nov 2015 05:05:21 +0000
"Xie, Huawei" <huawei.xie@intel.com> wrote:

> On 11/23/2015 12:07 PM, Stephen Hemminger wrote:
> > On Mon, 23 Nov 2015 03:46:31 +0000
> > "Xie, Huawei" <huawei.xie@intel.com> wrote:
> >
> >>> Why cannot we rely on the kernel zeroing the memory ?
> >>> If that behavior were to change, then we can zero out the memory
> >>> ourselves.  
> >> It is undocumented kernel behavior. My opinion is if not a big burden,
> >> zero out the needed memory ourselves, otherwise resort to this kernel
> >> behavior.
> > Really, I think it is more an oversight of missing documentation,
> > the kernel has always (and will continue) to zero out memory that is given
> > to a process. If it didn't it would be a massive security hole.
> Agree. I believe this behavior will not change in future. For the
> security issue, kernel could also set all bits like to 1. Just wonder if
> this is best practice and whether there are other user space programs
> rely on this behavior.
> 

Glibc almost certainly depends on this, because heap is grown by mmaping addtional
memory.