Added Mel and Vlastimil.
liuq <liuq131@xxxxxxxxxxxxxxx> writes:
> The current calculation of min_free_kbytes only uses ZONE_DMA and
> ZONE_NORMAL pages,but the ZONE_MOVABLE zone->_watermark[WMARK_MIN]
> will also divide part of min_free_kbytes.This will cause the min
> watermark of ZONE_NORMAL to be too small in the presence of ZONE_MOVEABLE.
This seems like a real problem per my understanding. Can you show the
contents of /proc/zoneinfo on a problem system?
But, per my understanding, min_free_kbytes are used for __GFP_HIGH and
PF_MEMALLOC allocations. While ZONE_MOVABLE will not be used for them
usually. So I think we should treat ZONE_MOVABLE as ZONE_HIGHMEM in
__setup_per_zone_wmarks().
Best Regards,
Huang, Ying
> Signed-off-by: liuq <liuq131@xxxxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 1 +
> mm/khugepaged.c | 2 +-
> mm/page_alloc.c | 15 ++++++++++++++-
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index cf3d0d673f6b..1f91d035bcaf 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -863,6 +863,7 @@ void split_page(struct page *page, unsigned int order);
> void folio_copy(struct folio *dst, struct folio *src);
>
> unsigned long nr_free_buffer_pages(void);
> +unsigned long nr_free_pagecache_pages(void);
>
> /*
> * Compound pages have a destructor function. Provide a
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 16be62d493cd..6632264b951c 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2342,7 +2342,7 @@ static void set_recommended_min_free_kbytes(void)
>
> /* don't ever allow to reserve more than 5% of the lowmem */
> recommended_min = min(recommended_min,
> - (unsigned long) nr_free_buffer_pages() / 20);
> + (unsigned long) nr_free_pagecache_pages() / 20);
> recommended_min <<= (PAGE_SHIFT-10);
>
> if (recommended_min > min_free_kbytes) {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e008a3df0485..489b564526dd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5775,6 +5775,19 @@ unsigned long nr_free_buffer_pages(void)
> }
> EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
>
> +/**
> + * nr_free_pagecache_pages - count number of pages beyond high watermark
> + *
> + * nr_free_pagecache_pages() counts the number of pages which are beyond the
> + * high watermark within all zones.
> + *
> + * Return: number of pages beyond high watermark within all zones.
> + */
> +unsigned long nr_free_pagecache_pages(void)
> +{
> + return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
> +}
> +
> static inline void show_node(struct zone *zone)
> {
> if (IS_ENABLED(CONFIG_NUMA))
> @@ -8651,7 +8664,7 @@ void calculate_min_free_kbytes(void)
> unsigned long lowmem_kbytes;
> int new_min_free_kbytes;
>
> - lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
> + lowmem_kbytes = nr_free_pagecache_pages() * (PAGE_SIZE >> 10);
> new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
>
> if (new_min_free_kbytes > user_min_free_kbytes)
