Re: [PATCH 2/3] Retry page fault when blocking on disk transfer.

["H. Peter Anvin" <hpa@zytor.com>]

On 10/05/2010 12:53 AM, Michel Lespinasse wrote:
> This change reduces mmap_sem hold times that are caused by waiting for
> disk transfers when accessing file mapped VMAs. It introduces the
> VM_FAULT_ALLOW_RETRY flag, which indicates that the call site wants
> mmap_sem to be released if blocking on a pending disk transfer.
> In that case, filemap_fault() returns the VM_FAULT_RETRY status bit
> and do_page_fault() will then re-acquire mmap_sem and retry the page fault.
> It is expected that the retry will hit the same page which will now be
> cached, and thus it will complete with a low mmap_sem hold time.
> 
> Signed-off-by: Michel Lespinasse <walken@google.com>
> ---
>  arch/x86/mm/fault.c |   38 ++++++++++++++++++++++++++------------
>  include/linux/mm.h  |    2 ++
>  mm/filemap.c        |   23 ++++++++++++++++++++++-
>  mm/memory.c         |    3 ++-
>  4 files changed, 52 insertions(+), 14 deletions(-)
> 

Acked-by: H. Peter Anvin <hpa@zytor.com>

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.