[dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary hugepage zero-filling
Stephen Hemminger
stephen at networkplumber.org
Wed Nov 18 20:09:06 CET 2015
On Wed, 18 Nov 2015 16:13:32 +0000
"Richardson, Bruce" <bruce.richardson at intel.com> wrote:
>
>
> > -----Original Message-----
> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Stephen Hemminger
> > Sent: Wednesday, November 18, 2015 4:00 PM
> > To: Xie, Huawei <huawei.xie at intel.com>
> > Cc: dev at 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 at 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.
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