Re: [Lse-tech] Re: Hugetlbpages in very large memory machines.......

[William Lee Irwin III <wli@holomorphy.com>]

On Sun, Mar 14, 2004 at 02:38:33AM -0600, Ray Bryant wrote:
> write mode and the mm->page_table_lock.  So not only does it take 500 s for
> the mmap() to return on our test system, but ps, top, etc all freeze for the
> duration.  Very irritating, especially on a 64 or 128 P system.
> My preference would be to do away with bugetlb_prefault() altogether.
> (If there was a MAP_NO_PREFAULT, we would have to make this the default on
> Altix to avoid the freeze problem mentioned above.  Can't have an arbitrary
> user locking up the system.)  As Andi pointed out, perhaps we can do some
> prereservation of huge pages so that we can return a ENONMEM to the mmap()
> if there are not enough huge pages to (lazily) be allocated to satisfy the
> request, but then still allocate the pages at fault time.  A simple count
> would suffice.

There is a patch which arranges to keep statistics ready in the mm so that
the mmap_sem need not be taken for /proc/ and furthermore renders
proc_pid_statm() nothing more than copying integers out of the mm that
I forward ported to 2.6.0-test*, originally by Ben LaHaise, that may
also be of interest to those concerned about tripping over other processes'
mmap_sem's in /proc/.


-- wli