diff mbox series

[RFC] mm: don't promote exclusive file folios of dying processes

Message ID 20250412085852.48524-1-21cnbao@gmail.com (mailing list archive)
State New
Headers show
Series [RFC] mm: don't promote exclusive file folios of dying processes | expand

Commit Message

Barry Song April 12, 2025, 8:58 a.m. UTC 
From: Barry Song <v-songbaohua@oppo.com>

Promoting exclusive file folios of a dying process is unnecessary and
harmful. For example, while Firefox is killed and LibreOffice is
launched, activating Firefox's young file-backed folios makes it
harder to reclaim memory that LibreOffice doesn't use at all.

An exiting process is unlikely to be restarted right away—it's
either terminated by the user or killed by the OOM handler.

Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
 mm/huge_memory.c |  4 ++--
 mm/internal.h    | 19 +++++++++++++++++++
 mm/memory.c      |  9 ++++++++-
 3 files changed, 29 insertions(+), 3 deletions(-)

Comments

Matthew Wilcox April 12, 2025, 3:48 p.m. UTC | #1 
On Sat, Apr 12, 2025 at 08:58:52PM +1200, Barry Song wrote:
> +		/*
> +		 * Skip marking exclusive file folios as accessed for processes that are
> +		 * exiting or have been reaped due to OOM. This prevents unnecessary
> +		 * promotion of folios that won't benefit the new process being launched.
> +		 */

Please wrap at 80 columns.

One easy way to achieve this is to pipe it through 'fmt -p \*'
Zi Yan April 12, 2025, 4:31 p.m. UTC | #2 
On 12 Apr 2025, at 4:58, Barry Song wrote:

> From: Barry Song <v-songbaohua@oppo.com>
>
> Promoting exclusive file folios of a dying process is unnecessary and
> harmful. For example, while Firefox is killed and LibreOffice is
> launched, activating Firefox's young file-backed folios makes it
> harder to reclaim memory that LibreOffice doesn't use at all.
>
> An exiting process is unlikely to be restarted right away—it's
> either terminated by the user or killed by the OOM handler.

The proposal looks reasonable to me. Do you have any performance number
about the improvement?

>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  mm/huge_memory.c |  4 ++--
>  mm/internal.h    | 19 +++++++++++++++++++
>  mm/memory.c      |  9 ++++++++-
>  3 files changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e97a97586478..05b83d2fcbb6 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2264,8 +2264,8 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  			 * Use flush_needed to indicate whether the PMD entry
>  			 * is present, instead of checking pmd_present() again.
>  			 */
> -			if (flush_needed && pmd_young(orig_pmd) &&
> -			    likely(vma_has_recency(vma)))
> +			if (!exclusive_folio_of_dying_process(folio, vma) && flush_needed &&
> +			    pmd_young(orig_pmd) && likely(vma_has_recency(vma)))
>  				folio_mark_accessed(folio);
>  		}
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 4e0ea83aaf1c..666de96a293d 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -11,6 +11,7 @@
>  #include <linux/khugepaged.h>
>  #include <linux/mm.h>
>  #include <linux/mm_inline.h>
> +#include <linux/oom.h>
>  #include <linux/pagemap.h>
>  #include <linux/pagewalk.h>
>  #include <linux/rmap.h>
> @@ -130,6 +131,24 @@ static inline int folio_nr_pages_mapped(const struct folio *folio)
>  	return atomic_read(&folio->_nr_pages_mapped) & FOLIO_PAGES_MAPPED;
>  }
>
> +/*
> + * Return true if a folio is exclusive and belongs to an exiting or
> + * oom-reaped process; otherwise, return false.
> + */
> +static inline bool exclusive_folio_of_dying_process(struct folio *folio,
> +		struct vm_area_struct *vma)
> +{
> +	if (folio_maybe_mapped_shared(folio))
> +		return false;
> +
> +	if (!atomic_read(&vma->vm_mm->mm_users))
> +		return true;
> +	if (check_stable_address_space(vma->vm_mm))
> +		return true;
> +
> +	return false;
> +}
> +
>  /*
>   * Retrieve the first entry of a folio based on a provided entry within the
>   * folio. We cannot rely on folio->swap as there is no guarantee that it has
> diff --git a/mm/memory.c b/mm/memory.c
> index b9e8443aaa86..cab69275e473 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1515,7 +1515,14 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb,
>  				*force_flush = true;
>  			}
>  		}
> -		if (pte_young(ptent) && likely(vma_has_recency(vma)))
> +
> +		/*
> +		 * Skip marking exclusive file folios as accessed for processes that are
> +		 * exiting or have been reaped due to OOM. This prevents unnecessary
> +		 * promotion of folios that won't benefit the new process being launched.
> +		 */
> +		if (!exclusive_folio_of_dying_process(folio, vma) && pte_young(ptent) &&
> +				likely(vma_has_recency(vma)))
>  			folio_mark_accessed(folio);
>  		rss[mm_counter(folio)] -= nr;
>  	} else {
> -- 
> 2.39.3 (Apple Git-146)


--
Best Regards,
Yan, Zi
diff mbox series

Patch

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e97a97586478..05b83d2fcbb6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2264,8 +2264,8 @@  int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			 * Use flush_needed to indicate whether the PMD entry
 			 * is present, instead of checking pmd_present() again.
 			 */
-			if (flush_needed && pmd_young(orig_pmd) &&
-			    likely(vma_has_recency(vma)))
+			if (!exclusive_folio_of_dying_process(folio, vma) && flush_needed &&
+			    pmd_young(orig_pmd) && likely(vma_has_recency(vma)))
 				folio_mark_accessed(folio);
 		}
 
diff --git a/mm/internal.h b/mm/internal.h
index 4e0ea83aaf1c..666de96a293d 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -11,6 +11,7 @@ 
 #include <linux/khugepaged.h>
 #include <linux/mm.h>
 #include <linux/mm_inline.h>
+#include <linux/oom.h>
 #include <linux/pagemap.h>
 #include <linux/pagewalk.h>
 #include <linux/rmap.h>
@@ -130,6 +131,24 @@  static inline int folio_nr_pages_mapped(const struct folio *folio)
 	return atomic_read(&folio->_nr_pages_mapped) & FOLIO_PAGES_MAPPED;
 }
 
+/*
+ * Return true if a folio is exclusive and belongs to an exiting or
+ * oom-reaped process; otherwise, return false.
+ */
+static inline bool exclusive_folio_of_dying_process(struct folio *folio,
+		struct vm_area_struct *vma)
+{
+	if (folio_maybe_mapped_shared(folio))
+		return false;
+
+	if (!atomic_read(&vma->vm_mm->mm_users))
+		return true;
+	if (check_stable_address_space(vma->vm_mm))
+		return true;
+
+	return false;
+}
+
 /*
  * Retrieve the first entry of a folio based on a provided entry within the
  * folio. We cannot rely on folio->swap as there is no guarantee that it has
diff --git a/mm/memory.c b/mm/memory.c
index b9e8443aaa86..cab69275e473 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1515,7 +1515,14 @@  static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb,
 				*force_flush = true;
 			}
 		}
-		if (pte_young(ptent) && likely(vma_has_recency(vma)))
+
+		/*
+		 * Skip marking exclusive file folios as accessed for processes that are
+		 * exiting or have been reaped due to OOM. This prevents unnecessary
+		 * promotion of folios that won't benefit the new process being launched.
+		 */
+		if (!exclusive_folio_of_dying_process(folio, vma) && pte_young(ptent) &&
+				likely(vma_has_recency(vma)))
 			folio_mark_accessed(folio);
 		rss[mm_counter(folio)] -= nr;
 	} else {