1 files changed, 30 insertions, 0 deletions
diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index e46f7a6917f9..c75f6f24f2d5 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -377,3 +377,33 @@ static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
 	/* no extra restriction */
 	return 0;
 }
+
+/**
+ * pcpu_should_reclaim_chunk - determine if a chunk should go into reclaim
+ * @chunk: chunk of interest
+ *
+ * This is the entry point for percpu reclaim.  If a chunk qualifies, it is then
+ * isolated and managed in separate lists at the back of pcpu_slot: sidelined
+ * and to_depopulate respectively.  The to_depopulate list holds chunks slated
+ * for depopulation.  They no longer contribute to pcpu_nr_empty_pop_pages once
+ * they are on this list.  Once depopulated, they are moved onto the sidelined
+ * list which enables them to be pulled back in for allocation if no other chunk
+ * can suffice the allocation.
+ */
+static bool pcpu_should_reclaim_chunk(struct pcpu_chunk *chunk)
+{
+	/* do not reclaim either the first chunk or reserved chunk */
+	if (chunk == pcpu_first_chunk || chunk == pcpu_reserved_chunk)
+		return false;
+
+	/*
+	 * If it is isolated, it may be on the sidelined list so move it back to
+	 * the to_depopulate list.  If we hit at least 1/4 pages empty pages AND
+	 * there is no system-wide shortage of empty pages aside from this
+	 * chunk, move it to the to_depopulate list.
+	 */
+	return ((chunk->isolated && chunk->nr_empty_pop_pages) ||
+		(pcpu_nr_empty_pop_pages[pcpu_chunk_type(chunk)] >
+		 PCPU_EMPTY_POP_PAGES_HIGH + chunk->nr_empty_pop_pages &&
+		chunk->nr_empty_pop_pages >= chunk->nr_pages / 4));
+}