Re: [Xen-devel] [PATCH 00/10] xen: arm: map normal memory as inner shareable, reduce scope of various barriers

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

I forgot to add an "RFC" to the subject line. I'm sure I don't need to
point out that this isn't for 4.3!

On Fri, 2013-06-28 at 17:10 +0100, Ian Campbell wrote:
> Currently Xen maps all RAM as Outer-Shareable, since that seemed like
> the most conservative option early on when we didn't really know what
> Inner- vs. Outer-Shareable meant. However we have long suspected that
> actually Inner-Shareable would be the correct type to use.
> 
> After reading the docs many times, getting more confused each time, I
> finally got a reasonable explanation from a man (and a dog) down the
> pub: Inner-Shareable == the processors in an SMP system, while
> Outer-Shareable == devices. (NB: Not a random man, he knew what he was
> talking about...). With that in mind switch all of Xen's memory mapping,
> page table walks, TLB flushes and an appropriate subset of the barriers
> to be inner shareable.
> 
> In addition I have switched barriers to use the correct read/write/any
> variants for their types. Note that I have only tackled the generic
> mb/rmb/wmb and smp_* barriers (mainly used by common code) here. There
> are also quite a few open-coded full-system dsb's in the arch code which
> I will look at separately (10 patches is quite enough for now). Since
> those deal with e.g. pagetable updates they will be fun ;-)
> 
> I have tested this series on Cortex A15 and AEMv8 fast models in both
> cases with 2 CPUs and I can start a guest in both cases. I have not
> tested on any real hardware at all.
> 
> These changes should result in a performance improvement, although only
> having models to go on I haven't actually bothered to measure.
> 
> I would appreciate anyone with access to real hardware giving it a go. I
> have pushed the patches to:
> 
>         git://xenbits.xen.org/people/ianc/xen.git inner-shareable-v1
>         
>         
> Ian Campbell (10):
>       xen: arm: map memory as inner shareable.
>       xen: arm: Only upgrade guest barriers to inner shareable.
>       xen: arm: reduce instruction cache and tlb flushes to inner-shareable.
>       xen: arm: consolidate barrier definitions
>       xen: use SMP barrier in common code dealing with shared memory protocols
>       xen: arm: Use SMP barriers when that is all which is required.
>       xen: arm: Use dmb for smp barriers
>       xen: arm: add scope to dsb and dmb macros
>       xen: arm: weaken SMP barriers to inner shareable.
>       xen: arm: use more specific barriers for read and write barriers.
> 
>  xen/arch/arm/arm32/head.S            |    8 +++---
>  xen/arch/arm/arm64/head.S            |    8 +++---
>  xen/arch/arm/domain.c                |    2 +-
>  xen/arch/arm/gic.c                   |    8 +++---
>  xen/arch/arm/mm.c                    |   28 ++++++++++------------
>  xen/arch/arm/platforms/vexpress.c    |    6 ++--
>  xen/arch/arm/smpboot.c               |    6 ++--
>  xen/arch/arm/time.c                  |    2 +-
>  xen/arch/arm/traps.c                 |    2 +-
>  xen/common/domain.c                  |    2 +-
>  xen/common/domctl.c                  |    2 +-
>  xen/common/grant_table.c             |    4 +-
>  xen/common/page_alloc.c              |    2 +-
>  xen/common/smp.c                     |    4 +-
>  xen/common/spinlock.c                |    6 ++--
>  xen/common/tmem_xen.c                |   10 ++++----
>  xen/common/trace.c                   |    8 +++---
>  xen/drivers/char/console.c           |    2 +-
>  xen/drivers/video/arm_hdlcd.c        |    2 +-
>  xen/include/asm-arm/arm32/flushtlb.h |   12 +++++-----
>  xen/include/asm-arm/arm32/io.h       |    4 +-
>  xen/include/asm-arm/arm32/page.h     |   12 +++++-----
>  xen/include/asm-arm/arm32/system.h   |   16 -------------
>  xen/include/asm-arm/arm64/flushtlb.h |    4 +-
>  xen/include/asm-arm/arm64/io.h       |    4 +-
>  xen/include/asm-arm/arm64/page.h     |   10 ++++----
>  xen/include/asm-arm/arm64/system.h   |   17 -------------
>  xen/include/asm-arm/page.h           |   42 
> +++++++++++++++++++++++++++++-----
>  xen/include/asm-arm/system.h         |   21 +++++++++++++++++
>  xen/include/xen/event.h              |    4 +-
>  xen/xsm/flask/ss/sidtab.c            |    4 +-
>  31 files changed, 139 insertions(+), 123 deletions(-)
> 
> Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel