linux-kernel - Re: [PATCH v1 1/2] mm/highmem: reimplement totalhigh

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Date: Fri, 7 Jun 2024 23:04:53 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
 Wei Yang <richard.weiyang@...il.com>
Subject: Re: [PATCH v1 1/2] mm/highmem: reimplement totalhigh_pages() by
 walking zones

On 07.06.24 10:37, David Hildenbrand wrote:
> Can we get rid of the highmem ifdef in adjust_managed_page_count()?
> Likely yes: we don't have that many totalhigh_pages() users, and they
> all don't seem to be very performance critical.
> 
> So let's implement totalhigh_pages() like nr_free_highpages(),
> collecting information from all zones. This is now similar to what we do
> in si_meminfo_node() to collect the per-node highmem page count.
> 
> In the common case (single node, 3-4 zones), we really shouldn't care.
> We could optimize a bit further (only walk ZONE_HIGHMEM and ZONE_MOVABLE
> if required), but there doesn't seem a real need for that.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>   include/linux/highmem-internal.h |  9 ++-------
>   mm/highmem.c                     | 16 +++++++++++++---
>   mm/page_alloc.c                  |  4 ----
>   3 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
> index a3028e400a9c6..65f865fbbac04 100644
> --- a/include/linux/highmem-internal.h
> +++ b/include/linux/highmem-internal.h
> @@ -132,7 +132,7 @@ static inline void __kunmap_atomic(const void *addr)
>   }
>   
>   unsigned int __nr_free_highpages(void);
> -extern atomic_long_t _totalhigh_pages;
> +unsigned long __totalhigh_pages(void);
>   
>   static inline unsigned int nr_free_highpages(void)
>   {
> @@ -141,12 +141,7 @@ static inline unsigned int nr_free_highpages(void)
>   
>   static inline unsigned long totalhigh_pages(void)
>   {
> -	return (unsigned long)atomic_long_read(&_totalhigh_pages);
> -}
> -
> -static inline void totalhigh_pages_add(long count)
> -{
> -	atomic_long_add(count, &_totalhigh_pages);
> +	return __totalhigh_pages();
>   }
>   
>   static inline bool is_kmap_addr(const void *x)
> diff --git a/mm/highmem.c b/mm/highmem.c
> index bd48ba445dd41..3c4e9f8c26dcd 100644
> --- a/mm/highmem.c
> +++ b/mm/highmem.c
> @@ -111,9 +111,6 @@ static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
>   }
>   #endif
>   
> -atomic_long_t _totalhigh_pages __read_mostly;
> -EXPORT_SYMBOL(_totalhigh_pages);
> -
>   unsigned int __nr_free_highpages(void)
>   {
>   	struct zone *zone;
> @@ -127,6 +124,19 @@ unsigned int __nr_free_highpages(void)
>   	return pages;
>   }
>   
> +unsigned long __totalhigh_pages(void)
> +{
> +	unsigned long pages = 0;
> +	struct zone *zone;
> +
> +	for_each_populated_zone(zone) {
> +		if (is_highmem(zone))
> +			pages += zone_managed_pages(zone);
> +	}
> +
> +	return pages;
> +}
> +

Another (later than usual, but better late than never) build bot complaint:

diff --git a/mm/highmem.c b/mm/highmem.c
index 3c4e9f8c26dcd..b14771fb05ed1 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -136,6 +136,7 @@ unsigned long __totalhigh_pages(void)
  
         return pages;
  }
+EXPORT_SYMBOL(__totalhigh_pages);
  
  static int pkmap_count[LAST_PKMAP];
  static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);

-- 
Cheers,

David / dhildenb