Re: must-fix list for 2.6.0

[William Lee Irwin III]

On Tue, Apr 29, 2003 at 03:57:31PM -0700, Andrew Morton wrote:
> mm/
> ---
> - Overcommit accounting gets wrong answers
>   - underestimates reclaimable slab, gives bogus failures when
>     dcache&icache are large.
>   - gets confused by reclaimable-but-not-freed truncated ext3 pages. 
>     Lame fix exists in -mm.
> - Proper user level no overcommit also requires a root margin adding

I didn't notice anything specific here about sys_remap_file_pages() vs.
truncate() (sans objrmap); did a fix fly by that I didn't notice,
or was it less of an issue than I thought it was?

Also, the OOM killer fails to check lowmem; basically it just needs
-       if (nr_swap_pages > 0)
+       if (nr_swap_pages > 0 && nr_free_buffer_pages() > 0)

With that in addition to the OOM killer locking patch I posted and
another to completely eliminate mm-less processes from consideration
64GB ia32 (with, of course, my oversized out-of-tree patch) recovers
from OOM instead of deadlocking after a mass-killing with swap online.
Not that I'd consider 64GB ia32 a supported platform for 2.5/2.6 (it's
a design limitation IMHO); it merely "stresses the OOM killer harder"
for the purposes of this discussion. Some kind of investigation is
probably needed to determine why eliminating mm-less processes from
consideration is necessary to obtain the desired behavior.

I'd be interested in more detailed descriptions of the user-level no
overcommit, dcacheicache, and truncated ext3 page issues after Thursday.

On Tue, Apr 29, 2003 at 03:57:31PM -0700, Andrew Morton wrote:
> mm/
> ---
> - objrmap: concerns over page reclaim performance at high sharing levels,
>   and interoperation with nonlinear mappings is hairy.
> - Readd and make /proc/sys/vm/freepages writable again so that boxes can be
>   tuned for heavy interrupt load.

The latter sounds easy to address. It actually sounds like a 2.4.x
compatibility fix.

-- wli