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

Richardson, Bruce bruce.richardson at intel.com
Wed Nov 18 17:13:32 CET 2015



> -----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


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