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Date:   Mon, 22 May 2023 11:20:57 +0000
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Subject: [PATCH mm-unstable 3/4] mm: multi-gen LRU: add helpers in page table walks
From:   "T.J. Alumbaugh" <talumbau@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Yuanchu Xie <yuanchu@google.com>, Yu Zhao <yuzhao@google.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-mm@google.com, "T.J. Alumbaugh" <talumbau@google.com>
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Add helpers to page table walking code:
 - Clarifies intent via name "should_walk_mmu" and "should_clear_pmd_young"
 - Avoids repeating same logic in two places

Signed-off-by: T.J. Alumbaugh <talumbau@google.com>
---
 mm/vmscan.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e088db138f5f..ad0f589d32e6 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3234,6 +3234,16 @@ DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
 #define get_cap(cap)	static_branch_unlikely(&lru_gen_caps[cap])
 #endif
 
+static bool should_walk_mmu(void)
+{
+	return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK);
+}
+
+static bool should_clear_pmd_young(void)
+{
+	return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG);
+}
+
 /******************************************************************************
  *                          shorthand helpers
  ******************************************************************************/
@@ -4098,7 +4108,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
 			goto next;
 
 		if (!pmd_trans_huge(pmd[i])) {
-			if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG))
+			if (should_clear_pmd_young())
 				pmdp_test_and_clear_young(vma, addr, pmd + i);
 			goto next;
 		}
@@ -4191,7 +4201,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 #endif
 		walk->mm_stats[MM_NONLEAF_TOTAL]++;
 
-		if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG)) {
+		if (should_clear_pmd_young()) {
 			if (!pmd_young(val))
 				continue;
 
@@ -4493,7 +4503,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	 * handful of PTEs. Spreading the work out over a period of time usually
 	 * is less efficient, but it avoids bursty page faults.
 	 */
-	if (!arch_has_hw_pte_young() || !get_cap(LRU_GEN_MM_WALK)) {
+	if (!should_walk_mmu()) {
 		success = iterate_mm_list_nowalk(lruvec, max_seq);
 		goto done;
 	}
@@ -5730,10 +5740,10 @@ static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, c
 	if (get_cap(LRU_GEN_CORE))
 		caps |= BIT(LRU_GEN_CORE);
 
-	if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))
+	if (should_walk_mmu())
 		caps |= BIT(LRU_GEN_MM_WALK);
 
-	if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG))
+	if (should_clear_pmd_young())
 		caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
 
 	return sysfs_emit(buf, "0x%04x\n", caps);
-- 
2.40.1.698.g37aff9b760-goog