linux-kernel - Re: [PATCH v9 1/3] mm: Shuffle initial free memory to improve memory-side-cache utilization

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Date:   Wed, 30 Jan 2019 10:30:16 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 1/3] mm: Shuffle initial free memory to improve
 memory-side-cache utilization

On Tue, Jan 29, 2019 at 10:49 PM Mike Rapoport <rppt@...ux.ibm.com> wrote:
>
> On Tue, Jan 29, 2019 at 09:02:16PM -0800, Dan Williams wrote:
> > Randomization of the page allocator improves the average utilization of
> > a direct-mapped memory-side-cache. Memory side caching is a platform
> > capability that Linux has been previously exposed to in HPC
> > (high-performance computing) environments on specialty platforms. In
> > that instance it was a smaller pool of high-bandwidth-memory relative to
> > higher-capacity / lower-bandwidth DRAM. Now, this capability is going to
> > be found on general purpose server platforms where DRAM is a cache in
> > front of higher latency persistent memory [1].
>
> [ ... ]
>
> > Cc: Michal Hocko <mhocko@...e.com>
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Cc: Mike Rapoport <rppt@...ux.ibm.com>
> > Reviewed-by: Kees Cook <keescook@...omium.org>
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > ---
> >  include/linux/list.h    |   17 ++++
> >  include/linux/mmzone.h  |    4 +
> >  include/linux/shuffle.h |   45 +++++++++++
> >  init/Kconfig            |   23 ++++++
> >  mm/Makefile             |    7 ++
> >  mm/memblock.c           |    1
> >  mm/memory_hotplug.c     |    3 +
> >  mm/page_alloc.c         |    6 +-
> >  mm/shuffle.c            |  188 +++++++++++++++++++++++++++++++++++++++++++++++
> >  9 files changed, 292 insertions(+), 2 deletions(-)
> >  create mode 100644 include/linux/shuffle.h
> >  create mode 100644 mm/shuffle.c
>
> ...
>
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index 022d4cbb3618..c0cfbfae4a03 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/poison.h>
> >  #include <linux/pfn.h>
> >  #include <linux/debugfs.h>
> > +#include <linux/shuffle.h>
>
> Nit: does not seem to be required
>
> >  #include <linux/kmemleak.h>
> >  #include <linux/seq_file.h>
> >  #include <linux/memblock.h>

Good catch. Notch one more line saved in the incremental diffstat from
v8. I'll wait for Michal's thumbs up on the rest before re-spinning,
or perhaps Andrew can drop this line on applying?