Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation

From	Matthew Wilcox <willy@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation
Date	2016-01-22 15:40 +0100
Message-ID	<qTL2y-5iq-5@gated-at.bofh.it> (permalink)
References	<oeUAN-8oD-7@gated-at.bofh.it> <oeUAQ-8oD-59@gated-at.bofh.it> <qTsjg-I1-23@gated-at.bofh.it> <qTJDs-4tt-9@gated-at.bofh.it> <qTKg9-4IT-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Fri, Jan 22, 2016 at 01:48:08PM +0000, Chris Brandt wrote:
> I believe the motivation for the new DAX code was being able to
> read/write data directly to specific physical memory. However, with
> the AXFS file system, XIP file mapping was mostly beneficial for direct
> access to executable code pages, not data. Code pages were XIP-ed, and
> data pages were copied to RAM as normal. This results in a significant
> reduction in system RAM, especially when used with an XIP_KERNEL. In
> some systems, most of your RAM is eaten up by lots of code pages from
> big bloated shared libraries, not R/W data. (of course I'm talking about
> smaller embedded system here)

OK, I can't construct a failure case for read-only usages.  If you want
to put together a patch-set that re-enables DAX in a read-only way on
those architectures, I'm fine with that.

I think your time would be better spent fixing the read-write problems;
once we see persistent memory on the embedded platforms, we'll need that
code anyway.

Thread

Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation Jared Hulbert <jaredeh@gmail.com> - 2016-01-21 19:40 +0100
  RE: [PATCH v12 10/20] dax: Replace XIP documentation with DAX  documentation "Wilcox, Matthew R" <matthew.r.wilcox@intel.com> - 2016-01-22 14:10 +0100
    RE: [PATCH v12 10/20] dax: Replace XIP documentation with DAX  documentation Chris Brandt <Chris.Brandt@renesas.com> - 2016-01-22 14:50 +0100
      Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX  documentation Matthew Wilcox <willy@linux.intel.com> - 2016-01-22 15:40 +0100
    Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation Jared Hulbert <jaredeh@gmail.com> - 2016-01-24 10:10 +0100
      Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX  documentation Matthew Wilcox <willy@linux.intel.com> - 2016-01-25 18:00 +0100
        Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation Jared Hulbert <jaredeh@gmail.com> - 2016-01-25 22:20 +0100
          Re: [PATCH v12 10/20] dax: Replace XIP documentation with DAX documentation Jared Hulbert <jaredeh@gmail.com> - 2016-01-27 21:00 +0100

csiph-web