+ mm-page_alloc-make-the-annotations-of-available-memory-more-accurate.patch added to mm-unstable branch

+ mm-page_alloc-make-the-annotations-of-available-memory-more-accurate.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/page_alloc: make the annotations of available memory more accurate
has been added to the -mm mm-unstable branch.  Its filename is
     mm-page_alloc-make-the-annotations-of-available-memory-more-accurate.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-make-the-annotations-of-available-memory-more-accurate.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Yang Yang <yang.yang29@zte.com.cn>
Subject: mm/page_alloc: make the annotations of available memory more accurate
Date: Thu, 23 Jun 2022 02:08:34 +0000

Not all systems use swap, so estimating available memory would help to
prevent swapping or OOM of system that not use swap.

And we need to reserve some page cache to prevent swapping or thrashing. 
If somebody is accessing the pages in pagecache, and if too much would be
freed, most accesses might mean reading data from disk, i.e.  thrashing.

Link: https://lkml.kernel.org/r/20220623020833.972979-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-make-the-annotations-of-available-memory-more-accurate
+++ a/mm/page_alloc.c
@@ -5879,14 +5879,14 @@ long si_mem_available(void)
 
 	/*
 	 * Estimate the amount of memory available for userspace allocations,
-	 * without causing swapping.
+	 * without causing swapping or OOM.
 	 */
 	available = global_zone_page_state(NR_FREE_PAGES) - totalreserve_pages;
 
 	/*
 	 * Not all the page cache can be freed, otherwise the system will
-	 * start swapping. Assume at least half of the page cache, or the
-	 * low watermark worth of cache, needs to stay.
+	 * start swapping or thrashing. Assume at least half of the page
+	 * cache, or the low watermark worth of cache, needs to stay.
 	 */
 	pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
 	pagecache -= min(pagecache / 2, wmark_low);
_

Patches currently in -mm which might be from yang.yang29@zte.com.cn are

mm-page_alloc-make-the-annotations-of-available-memory-more-accurate.patch