Re: [PATCH] add a clear_pages function to clear pages of higher

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Tue, 5 Apr 2005 17:15:53 -0700 (PDT), Christoph Lameter <clameter@engr.sgi.com> said:

  Christoph> On Thu, 24 Mar 2005, David Mosberger wrote:
  >> That's definitely the case.  See my earlier post on this topic:

  >> http://www.gelato.unsw.edu.au/linux-ia64/0409/11012.html

  >> Unfortunately, nobody reported any results for larger machines
  >> and/or more interesting workloads, so the patch is in limbo at
  >> this time.  Clearly, if the CPU that's clearing the page is
  >> likely to use that same page soon after, it'd be useful to use
  >> temporal stores.

  Christoph> Here are some numbers using lmbench of temporal writes
  Christoph> vs. non temporal writes on ia64 (8p machine but lmbench
  Christoph> run only for one load). There seems to be some benefit
  Christoph> for fork/exec but overall this does not seem to be a
  Christoph> clear win. I suspect that the distinction between
  Christoph> temporal vs. nontemporal writes is be more beneficial on
  Christoph> machines with smaller pagesizes since the likelyhood that
  Christoph> most cachelines of a page are used soon is increased and
  Christoph> therefore hot zeroing is more beneficial.

What LMbench test other than fork/exec would you have expected to be
affected by this?  LMbench is not a good benchmark for this (remember:
it's a _micro_ benchmark).

	--david