On Wed, 30 Jul 2008, Andrew Morton wrote:

On Mon, 28 Jul 2008 12:17:10 -0700 Eric Munson [off-list ref] wrote:

quoted

Certain workloads benefit if their data or text segments are backed by
huge pages. The stack is no exception to this rule but there is no
mechanism currently that allows the backing of a stack reliably with
huge pages.  Doing this from userspace is excessively messy and has some
awkward restrictions.  Particularly on POWER where 256MB of address space
gets wasted if the stack is setup there.

This patch stack introduces a personality flag that indicates the kernel
should setup the stack as a hugetlbfs-backed region. A userspace utility
may set this flag then exec a process whose stack is to be backed by
hugetlb pages.

Eric Munson (5):
  Align stack boundaries based on personality
  Add shared and reservation control to hugetlb_file_setup
  Split boundary checking from body of do_munmap
  Build hugetlb backed process stacks
  [PPC] Setup stack memory segment for hugetlb pages

 arch/powerpc/mm/hugetlbpage.c |    6 +
 arch/powerpc/mm/slice.c       |   11 ++
 fs/exec.c                     |  209 ++++++++++++++++++++++++++++++++++++++---
 fs/hugetlbfs/inode.c          |   52 +++++++----
 include/asm-powerpc/hugetlb.h |    3 +
 include/linux/hugetlb.h       |   22 ++++-
 include/linux/mm.h            |    1 +
 include/linux/personality.h   |    3 +
 ipc/shm.c                     |    2 +-
 mm/mmap.c                     |   11 ++-
 10 files changed, 284 insertions(+), 36 deletions(-)

That all looks surprisingly straightforward.

Might there exist an x86 port which people can play with?

I have tested these patches on x86, x86_64, and ppc64, but not yet on ia64.
There is a user space utility that I have been using to test which would be
included in libhugetlbfs if this is merged into the kernel.  I will send it
out as a reply to this thread, performance numbers are also on the way.

-- 
Eric B Munson
IBM Linux Technology Center
ebmunson@us.ibm.com