Re: [mm][RFC][PATCH 0/11] mm accessor updates.

Andi Kleen
2009-12-16T10:11:21Z

On Wed, Dec 16, 2009 at 12:00:11PM +0900, KAMEZAWA Hiroyuki wrote:
> This is from Christoph Lameter's mm_accessor patch posted 5/Nov.
>
> Replacing all access to mm->mmap_sem with mm-accessor functions as
> mm_read_lock,
> mm_write_lock,
> etc...
>
> This kind of function allows us to improve page fault performance etc..
> For example, skil down_read(mmap_sem) in some situation.
> (as: http://marc.info/?l=linux-mm&m=125809791306459&w=2)

The problem is that it also slows down the writers, and we have
some workloads where writing is the bottleneck.

I don't think this is the right trade off at this time.

Also the patches didn't fare too well in testing unfortunately.

I suspect we'll rather need multiple locks split per address
space range.

-Andi

--
ak@linux.intel.com -- Speaking for myself only.