On Tue, 2005-10-04 at 01:41 +0800, Coywolf Qi Hunt wrote:
> Hello,
>
> In zone_watermark_ok(), the original algorithm seems not logical. This is a
> rework. Comments?
>
> Coywolf
>
>
> Signed-off-by: Coywolf Qi Hunt <[email protected]>
> ---
>
> page_alloc.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> --- 2.6.14-rc2-mm1/mm/page_alloc.c~orig 2005-09-29 20:37:07.000000000 +0800
> +++ 2.6.14-rc2-mm1/mm/page_alloc.c 2005-10-04 01:19:31.000000000 +0800
> @@ -772,7 +772,7 @@
> int zone_watermark_ok(struct zone *z, int order, unsigned long mark,
> int classzone_idx, int can_try_harder, int gfp_high)
> {
> - /* free_pages my go negative - that's OK */
> + /* free_pages may go negative - that's OK */
> long min = mark, free_pages = z->free_pages - (1 << order) + 1;
> int o;
>
Typo. Thanks.
> @@ -783,17 +783,12 @@
>
> if (free_pages <= min + z->lowmem_reserve[classzone_idx])
> return 0;
> - for (o = 0; o < order; o++) {
> - /* At the next order, this order's pages become unavailable */
> - free_pages -= z->free_area[o].nr_free << o;
>
> - /* Require fewer higher order pages to be free */
> - min >>= 1;
> -
> - if (free_pages <= min)
> - return 0;
> + for (o = order; o < MAX_ORDER; o++) {
> + if (z->free_area[o].nr_free)
> + return 1;
> }
> - return 1;
> + return 0;
> }
>
> static inline int
Well the original algorithm's intention is to include some watermarks
for higher order pages for eg. GFP_ATOMIC and PF_MEMALLOC. To that
goal I believe the algorithm is logical?
Yours is correct if our intention was simply to ensure _any_ higher
order page is available, however it is also redundant because rmqueue
will catch that for us. However, that is not the intention :)
Any reasons why it should be changed?
Thanks,
Nick
--
SUSE Labs, Novell Inc.
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