demand_paging: eviction: add kconfig CONFIG_EVICTION_TRACKING

arch/Kconfig

@@ -55,6 +55,8 @@ config ARM64
 	select ARCH_HAS_DIRECTED_IPIS
 	select ARCH_HAS_DEMAND_PAGING
 	select ARCH_HAS_DEMAND_MAPPING
+	select ARCH_SUPPORTS_EVICTION_TRACKING
+	select EVICTION_TRACKING if DEMAND_PAGING
 	help
 	  ARM64 (AArch64) architecture
 
@@ -694,6 +696,12 @@ config ARCH_SUPPORTS_ROM_START
 config ARCH_SUPPORTS_EMPTY_IRQ_SPURIOUS
 	bool
 
+config ARCH_SUPPORTS_EVICTION_TRACKING
+	bool
+	help
+	  Architecture code supports page tracking for eviction algorithms
+	  when demand paging is enabled.
+
 config ARCH_HAS_EXTRA_EXCEPTION_INFO
 	bool
 

doc/kernel/memory_management/demand_paging.rst

@@ -156,8 +156,12 @@ Two eviction algorithms are currently available:
   to the NRU code but also considerably more efficient. This is recommended for
   production use.
 
-To implement a new eviction algorithm, the five functions mentioned
-above must be implemented.
+To implement a new eviction algorithm, :c:func:`k_mem_paging_eviction_init()`
+and :c:func:`k_mem_paging_eviction_select()` must be implemented.
+If :kconfig:option:`CONFIG_EVICTION_TRACKING` is enabled for an algorithm,
+these additional functions must also be implemented,
+:c:func:`k_mem_paging_eviction_add()`, :c:func:`k_mem_paging_eviction_remove()`,
+:c:func:`k_mem_paging_eviction_accessed()`.
 
 Backing Store
 *************

include/zephyr/kernel/mm/demand_paging.h

@@ -217,6 +217,8 @@ __syscall void k_mem_paging_histogram_backing_store_page_out_get(
  * @{
  */
 
+#if defined(CONFIG_EVICTION_TRACKING) || defined(__DOXYGEN__)
+
 /**
  * Submit a page frame for eviction candidate tracking
  *
@@ -261,6 +263,25 @@ void k_mem_paging_eviction_remove(struct k_mem_page_frame *pf);
  */
 void k_mem_paging_eviction_accessed(uintptr_t phys);
 
+#else /* CONFIG_EVICTION_TRACKING || __DOXYGEN__ */
+
+static inline void k_mem_paging_eviction_add(struct k_mem_page_frame *pf)
+{
+	ARG_UNUSED(pf);
+}
+
+static inline void k_mem_paging_eviction_remove(struct k_mem_page_frame *pf)
+{
+	ARG_UNUSED(pf);
+}
+
+static inline void k_mem_paging_eviction_accessed(uintptr_t phys)
+{
+	ARG_UNUSED(phys);
+}
+
+#endif /* CONFIG_EVICTION_TRACKING || __DOXYGEN__ */
+
 /**
  * Select a page frame for eviction
  *

kernel/mmu.c

@@ -556,7 +556,7 @@
 	}
 	frame_mapped_set(pf, addr);
 #ifdef CONFIG_DEMAND_PAGING
-	if (!lock) {
+	if (IS_ENABLED(CONFIG_EVICTION_TRACKING) && (!lock)) {
 		k_mem_paging_eviction_add(pf);
 	}
 #endif
@@ -784,7 +784,8 @@
 
 			arch_mem_unmap(pos, CONFIG_MMU_PAGE_SIZE);
 #ifdef CONFIG_DEMAND_PAGING
-			if (!k_mem_page_frame_is_pinned(pf)) {
+			if (IS_ENABLED(CONFIG_EVICTION_TRACKING) &&
+			    (!k_mem_page_frame_is_pinned(pf))) {
 				k_mem_paging_eviction_remove(pf);
 			}
 #endif
@@ -1041,7 +1042,8 @@
 		} else {
 			k_mem_page_frame_clear(pf, K_MEM_PAGE_FRAME_PINNED);
 #ifdef CONFIG_DEMAND_PAGING
-			if (k_mem_page_frame_is_evictable(pf)) {
+			if (IS_ENABLED(CONFIG_EVICTION_TRACKING) &&
+			    k_mem_page_frame_is_evictable(pf)) {
 				k_mem_paging_eviction_add(pf);
 			}
 #endif
@@ -1147,10 +1149,13 @@
 #endif /* CONFIG_DEMAND_PAGING_TIMING_HISTOGRAM */
 	k_mem_paging_backing_store_init();
 	k_mem_paging_eviction_init();
-	/* start tracking evictable page installed above if any */
-	K_MEM_PAGE_FRAME_FOREACH(phys, pf) {
-		if (k_mem_page_frame_is_evictable(pf)) {
-			k_mem_paging_eviction_add(pf);
+
+	if (IS_ENABLED(CONFIG_EVICTION_TRACKING)) {
+		/* start tracking evictable page installed above if any */
+		K_MEM_PAGE_FRAME_FOREACH(phys, pf) {
+			if (k_mem_page_frame_is_evictable(pf)) {
+				k_mem_paging_eviction_add(pf);
+			}
 		}
 	}
 #endif /* CONFIG_DEMAND_PAGING */
@@ -1347,7 +1352,10 @@
 			return -ENOMEM;
 		}
 		arch_mem_page_out(k_mem_page_frame_to_virt(pf), *location_ptr);
-		k_mem_paging_eviction_remove(pf);
+
+		if (IS_ENABLED(CONFIG_EVICTION_TRACKING)) {
+			k_mem_paging_eviction_remove(pf);
+		}
 	} else {
 		/* Shouldn't happen unless this function is mis-used */
 		__ASSERT(!dirty, "un-mapped page determined to be dirty");
@@ -1683,7 +1691,9 @@
 
 			pf = k_mem_phys_to_page_frame(phys);
 			if (!k_mem_page_frame_is_pinned(pf)) {
-				k_mem_paging_eviction_remove(pf);
+				if (IS_ENABLED(CONFIG_EVICTION_TRACKING)) {
+					k_mem_paging_eviction_remove(pf);
+				}
 				k_mem_page_frame_set(pf, K_MEM_PAGE_FRAME_PINNED);
 			}
 		}
@@ -1738,7 +1748,7 @@
 
 	arch_mem_page_in(addr, k_mem_page_frame_to_phys(pf));
 	k_mem_paging_backing_store_page_finalize(pf, page_in_location);
-	if (!pin) {
+	if (IS_ENABLED(CONFIG_EVICTION_TRACKING) && (!pin)) {
 		k_mem_paging_eviction_add(pf);
 	}
 out:
@@ -1807,7 +1817,10 @@
 		pf = k_mem_phys_to_page_frame(phys);
 		if (k_mem_page_frame_is_pinned(pf)) {
 			k_mem_page_frame_clear(pf, K_MEM_PAGE_FRAME_PINNED);
-			k_mem_paging_eviction_add(pf);
+
+			if (IS_ENABLED(CONFIG_EVICTION_TRACKING)) {
+				k_mem_paging_eviction_add(pf);
+			}
 		}
 	}
 	k_spin_unlock(&z_mm_lock, key);

subsys/demand_paging/eviction/Kconfig

@@ -11,6 +11,7 @@ choice EVICTION_CHOICE
 
 config EVICTION_CUSTOM
 	bool "Custom eviction algorithm"
+	imply EVICTION_TRACKING
 	help
 	  This option is chosen when the eviction algorithm will be implemented
 	  by the application, instead of using one included in Zephyr.
@@ -30,6 +31,7 @@ config EVICTION_NRU
 
 config EVICTION_LRU
 	bool "Least Recently Used (LRU) page eviction algorithm"
+	select EVICTION_TRACKING
 	help
 	  This implements a Least Recently Used page eviction algorithm.
 	  Usage is tracked based on MMU protection making pages unaccessible
@@ -49,3 +51,11 @@ config EVICTION_NRU_PERIOD
 	  pages that are capable of being paged out. At eviction time, if a page
 	  still has the accessed property, it will be considered as recently used.
 endif # EVICTION_NRU
+
+config EVICTION_TRACKING
+	bool
+	depends on ARCH_SUPPORTS_EVICTION_TRACKING
+	help
+	  Selected by eviction algorithms which needs page tracking and need to
+	  implement the following functions: k_mem_paging_eviction_add(),
+	  k_mem_paging_eviction_remove() and k_mem_paging_eviction_accessed().

subsys/demand_paging/eviction/nru.c

@@ -111,8 +111,11 @@ void k_mem_paging_eviction_init(void)
 		      K_MSEC(CONFIG_EVICTION_NRU_PERIOD));
 }
 
+#ifdef CONFIG_EVICTION_TRACKING
 /*
- * unused interfaces
+ * Empty functions defined here so that architectures unconditionally
+ * implement eviction tracking can still use this algorithm for
+ * testing.
  */
 
 void k_mem_paging_eviction_add(struct k_mem_page_frame *pf)
@@ -129,3 +132,5 @@ void k_mem_paging_eviction_accessed(uintptr_t phys)
 {
 	ARG_UNUSED(phys);
 }
+
+#endif /* CONFIG_EVICTION_TRACKING */