Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1380480

Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings

Show all headers | View raw

On Thu, 14 Apr 2016 10:48:29 -0600 Toshi Kani <toshi.kani@hpe.com> wrote:

> When CONFIG_FS_DAX_PMD is set, DAX supports mmap() using pmd page
> size.  This feature relies on both mmap virtual address and FS
> block (i.e. physical address) to be aligned by the pmd page size.
> Users can use mkfs options to specify FS to align block allocations.
> However, aligning mmap address requires code changes to existing
> applications for providing a pmd-aligned address to mmap().
> 
> For instance, fio with "ioengine=mmap" performs I/Os with mmap() [1].
> It calls mmap() with a NULL address, which needs to be changed to
> provide a pmd-aligned address for testing with DAX pmd mappings.
> Changing all applications that call mmap() with NULL is undesirable.
> 
> This patch-set extends filesystems to align an mmap address for
> a DAX file so that unmodified applications can use DAX pmd mappings.

Matthew sounded unconvinced about the need for this patchset, but I
must say that

: The point is that we do not need to modify existing applications for using
: DAX PMD mappings.
: 
: For instance, fio with "ioengine=mmap" performs I/Os with mmap(). 
: https://github.com/caius/fio/blob/master/engines/mmap.c
: 
: With this change, unmodified fio can be used for testing with DAX PMD
: mappings.  There are many examples like this, and I do not think we want
: to modify all applications that we want to evaluate/test with.

sounds pretty convincing?


And if we go ahead with this, it looks like 4.7 material to me - it
affects ABI and we want to get that stabilized asap.  What do people
think?

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v3 0/2] Align mmap address for DAX pmd mappings Toshi Kani <toshi.kani@hpe.com> - 2016-04-14 19:00 +0200
  Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Andrew Morton <akpm@linux-foundation.org> - 2016-04-16 07:10 +0200
    Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Jan Kara <jack@suse.cz> - 2016-04-18 22:30 +0200
      Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Matthew Wilcox <willy@linux.intel.com> - 2016-04-19 20:30 +0200
        Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Toshi Kani <toshi.kani@hpe.com> - 2016-04-21 05:20 +0200
          Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Matthew Wilcox <willy@linux.intel.com> - 2016-04-21 09:10 +0200
            Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Mike Kravetz <mike.kravetz@oracle.com> - 2016-04-21 22:30 +0200
              Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Toshi Kani <toshi.kani@hpe.com> - 2016-04-22 01:50 +0200
                Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Matthew Wilcox <willy@linux.intel.com> - 2016-04-22 02:30 +0200
                Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Toshi Kani <toshi.kani@hpe.com> - 2016-04-22 03:00 +0200
            Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings Toshi Kani <toshi.kani@hpe.com> - 2016-04-22 01:40 +0200

csiph-web