Re: [PATCH v1 1/2] mm/highmem: reimplement totalhigh_pages() by walking zones

[Wei Yang]

On Fri, Jun 07, 2024 at 10:37:10AM +0200, 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@xxxxxxxxxx>

Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>---
> 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;
>+}
>+
> static int pkmap_count[LAST_PKMAP];
> static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
> 
>diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>index fc98082a9cf9c..2224965ada468 100644
>--- a/mm/page_alloc.c
>+++ b/mm/page_alloc.c
>@@ -5794,10 +5794,6 @@ void adjust_managed_page_count(struct page *page, long count)
> {
> 	atomic_long_add(count, &page_zone(page)->managed_pages);
> 	totalram_pages_add(count);
>-#ifdef CONFIG_HIGHMEM
>-	if (PageHighMem(page))
>-		totalhigh_pages_add(count);
>-#endif
> }
> EXPORT_SYMBOL(adjust_managed_page_count);
> 
>-- 
>2.45.1

-- 
Wei Yang
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