Re: 2.5.73-mm2

Andrew Morton
2003-07-01T02:14:56Z

William Lee Irwin III <wli@holomorphy.com> wrote:
>
> @@ -217,9 +217,9 @@ void out_of_memory(void)
> unsigned long now, since;
>
> /*
> - * Enough swap space left? Not OOM.
> + * Enough swap space and ZONE_NORMAL left? Not OOM.
> */
> - if (nr_swap_pages > 0)
> + if (nr_swap_pages > 0 && nr_free_buffer_pages() + nr_used_low_pages() > 0)
> return;

a) if someone is trying to allocate some ZONE_DMA pages and there are
still swappable or free ZONE_NORMAL pages, nobody gets killed.

b) If there are free ZONE_NORMAL pages then why on earth did we call
out_of_memory()? Does nr_free_buffer_pages() ever return non-zero in
here? It will do so for a ZONE_DMA allocation, but you're not doing
them...

Generally, I'm thinking that this test should just be removed. It is
the responsibility of try_to_free_pages() to work out whether the
allocation can succeed.

If try_to_free_pages() calls out_of_memory() when there are still
swappable, reclaimable or free pages in the relevant zones then
try_to_free_pages() goofed, and needs mending. out_of_memory()
shouldn't be cleaning up after try_to_free_pages()'s mistakes.

I have a bad feeling that it _will_ goof. A long time ago I looked
at the amount of scanning we're doing in there and decided that it
was way overkill and reduced it by a lot. I may have gone overboard.

So how's about I and thy take that test out, see how things get along?