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authorYang Yang <yang.yang29@zte.com.cn>2023-04-13 16:34:49 +0800
committerAndrew Morton <akpm@linux-foundation.org>2023-04-18 16:30:11 -0700
commited8f3f999e9270ccc542ac44e237e389a2687a9e (patch)
tree01870b2febf6ec91ecfedf47a9c1ad9d54de7786 /mm/workingset.c
parent1f6ab566cb3be9e8292e34b89e8be83d75aa232e (diff)
mm: workingset: update description of the source file
The calculation of workingset size is the core logic of handling refault, it had been updated several times[1][2] after workingset.c was created[3]. But the description hadn't been updated accordingly, this mismatch may confuse the readers. So we update the description to make it consistent to the code. [1] commit 34e58cac6d8f ("mm: workingset: let cache workingset challenge anon") [2] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU") [3] commit a528910e12ec ("mm: thrash detection-based file cache sizing") Link: https://lkml.kernel.org/r/202304131634494948454@zte.com.cn Signed-off-by: Yang Yang <yang.yang29@zte.com.cn> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/workingset.c')
-rw-r--r--mm/workingset.c23
1 files changed, 17 insertions, 6 deletions
diff --git a/mm/workingset.c b/mm/workingset.c
index 3025beee9b34..817758951886 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -111,9 +111,20 @@
*
* NR_inactive + (R - E) <= NR_inactive + NR_active
*
- * which can be further simplified to
+ * If we have swap we should consider about NR_inactive_anon and
+ * NR_active_anon, so for page cache and anonymous respectively:
*
- * (R - E) <= NR_active
+ * NR_inactive_file + (R - E) <= NR_inactive_file + NR_active_file
+ * + NR_inactive_anon + NR_active_anon
+ *
+ * NR_inactive_anon + (R - E) <= NR_inactive_anon + NR_active_anon
+ * + NR_inactive_file + NR_active_file
+ *
+ * Which can be further simplified to:
+ *
+ * (R - E) <= NR_active_file + NR_inactive_anon + NR_active_anon
+ *
+ * (R - E) <= NR_active_anon + NR_inactive_file + NR_active_file
*
* Put into words, the refault distance (out-of-cache) can be seen as
* a deficit in inactive list space (in-cache). If the inactive list
@@ -130,14 +141,14 @@
* are no longer in active use.
*
* So when a refault distance of (R - E) is observed and there are at
- * least (R - E) active pages, the refaulting page is activated
- * optimistically in the hope that (R - E) active pages are actually
+ * least (R - E) pages in the userspace workingset, the refaulting page
+ * is activated optimistically in the hope that (R - E) pages are actually
* used less frequently than the refaulting page - or even not used at
* all anymore.
*
* That means if inactive cache is refaulting with a suitable refault
* distance, we assume the cache workingset is transitioning and put
- * pressure on the current active list.
+ * pressure on the current workingset.
*
* If this is wrong and demotion kicks in, the pages which are truly
* used more frequently will be reactivated while the less frequently
@@ -469,7 +480,7 @@ void workingset_refault(struct folio *folio, void *shadow)
* don't activate pages that couldn't stay resident even if
* all the memory was available to the workingset. Whether
* workingset competition needs to consider anon or not depends
- * on having swap.
+ * on having free swap space.
*/
workingset_size = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE);
if (!file) {