Re: + mm-page_owner-align-with-pageblock_nr-pages.patch added to -mm tree

Re: + mm-page_owner-align-with-pageblock_nr-pages.patch added to -mm tree

[Michal Hocko]

On Tue 19-07-16 12:08:30, Andrew Morton wrote:
> From: zhong jiang <zhongjiang@huawei.com>
> Subject: mm/page_owner: align with pageblock_nr pages
> 
> When pfn_valid(pfn) return false, pfn should be align with
> pageblock_nr_pages other than MAX_ORDER_NR_PAGES in init_pages_in_zone,
> because the skipped 2M may be valid pfn, as a result, early allocated
> count will not be accurate.
> 
> Link: http://lkml.kernel.org/r/1468938136-24228-1-git-send-email-zhongjiang@huawei.com
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

So I can still see this in the mmomt tree. We have discussed that
briefly and I am not sure this is an improvement or just replaces
a confused code by a differently confused one. See
http://lkml.kernel.org/r/8a4e54f2-23ed-f20f-c0da-e9412f52b606@suse.cz

What we haven't heard of yet is whether this patch actually fixes any
real problem. If not I would prefer not to make this kind of changes and
rather rework the function and co. to work with all the supported memory
models with different possible holes.

> ---
> 
>  mm/page_owner.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff -puN mm/page_owner.c~mm-page_owner-align-with-pageblock_nr-pages mm/page_owner.c
> --- a/mm/page_owner.c~mm-page_owner-align-with-pageblock_nr-pages
> +++ a/mm/page_owner.c
> @@ -417,7 +417,7 @@ static void init_pages_in_zone(pg_data_t
>  	 */
>  	for (; pfn < end_pfn; ) {
>  		if (!pfn_valid(pfn)) {
> -			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
> +			pfn = ALIGN(pfn + 1, pageblock_nr_pages);
>  			continue;
>  		}
>  
> _
> 
> Patches currently in -mm which might be from zhongjiang@huawei.com are
> 
> mm-update-the-comment-in-__isolate_free_page.patch
> mm-page_owner-align-with-pageblock_nr-pages.patch

-- 
Michal Hocko
SUSE Labs

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