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

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 18 Nov 2015 16:13:32 +0000
"Richardson, Bruce" <bruce.richardson@intel.com> wrote:

> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
> > Sent: Wednesday, November 18, 2015 4:00 PM
> > To: Xie, Huawei <huawei.xie@intel.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary
> > hugepage zero-filling
> > 
> > On Wed, 18 Nov 2015 12:07:54 +0000
> > "Xie, Huawei" <huawei.xie@intel.com> wrote:
> > 
> > > >>> 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 all new pages are zero, why does DPDK have to pre-touch the pages at
> > all?
> 
> The pages won't actually be mapped into the processes address space until accessed. 
> 
> /Bruce

Isn't that what mmap MAP_POPULATE flag (not currently used) will do.