On Wed, Nov 18, 2015 at 11:09:06AM -0800, Stephen Hemminger wrote: > 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.
Hadn't seen that flag before, but it does indeed look to do exactly what we want. /Bruce
