diff mbox series

[2/4] workingset: refactor LRU refault to expose refault recency check

Message ID 20221115182901.2755368-3-nphamcs@gmail.com (mailing list archive)
State New
Headers show
Series cachestat: a new syscall for page cache state of files | expand

Commit Message

Nhat Pham Nov. 15, 2022, 6:28 p.m. UTC 
In preparation for computing recently evicted pages in cachestat,
refactor workingset_refault and lru_gen_refault to expose a helper
function that would test if an evicted page is recently evicted.

Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 include/linux/swap.h |   1 +
 mm/workingset.c      | 141 +++++++++++++++++++++++++++++--------------
 2 files changed, 98 insertions(+), 44 deletions(-)

Comments

kernel test robot Nov. 16, 2022, 7:02 a.m. UTC | #1 
Hi Nhat,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on shuah-kselftest/next]
[also build test WARNING on shuah-kselftest/fixes tip/x86/asm arnd-asm-generic/master linus/master v6.1-rc5 next-20221115]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Nhat-Pham/cachestat-a-new-syscall-for-page-cache-state-of-files/20221116-023042
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
patch link:    https://lore.kernel.org/r/20221115182901.2755368-3-nphamcs%40gmail.com
patch subject: [PATCH 2/4] workingset: refactor LRU refault to expose refault recency check
config: m68k-allyesconfig
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/21cc57c8a41260cb193875b3d8668b1ef57cf0c2
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Nhat-Pham/cachestat-a-new-syscall-for-page-cache-state-of-files/20221116-023042
        git checkout 21cc57c8a41260cb193875b3d8668b1ef57cf0c2
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> mm/workingset.c:248: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Test if the folio is recently evicted.
   mm/workingset.c:408: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Test if the folio is recently evicted by checking if


vim +248 mm/workingset.c

   246	
   247	/**
 > 248	 * Test if the folio is recently evicted.
   249	 *
   250	 * As a side effect, also populates the references with
   251	 * values unpacked from the shadow of the evicted folio.
   252	 */
   253	static bool lru_gen_test_recent(void *shadow, bool file, int *memcgid,
   254		struct pglist_data **pgdat, unsigned long *token, bool *workingset)
   255	{
   256		struct mem_cgroup *eviction_memcg;
   257		struct lruvec *lruvec;
   258		struct lru_gen_struct *lrugen;
   259		unsigned long min_seq;
   260	
   261		unpack_shadow(shadow, memcgid, pgdat, token, workingset);
   262		eviction_memcg = mem_cgroup_from_id(*memcgid);
   263	
   264		lruvec = mem_cgroup_lruvec(eviction_memcg, *pgdat);
   265		lrugen = &lruvec->lrugen;
   266	
   267		min_seq = READ_ONCE(lrugen->min_seq[file]);
   268		return !((*token >> LRU_REFS_WIDTH) != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)));
   269	}
   270
diff mbox series

Patch

diff --git a/include/linux/swap.h b/include/linux/swap.h
index a18cf4b7c724..dae6f6f955eb 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -361,6 +361,7 @@  static inline void folio_set_swap_entry(struct folio *folio, swp_entry_t entry)
 }
 
 /* linux/mm/workingset.c */
+bool workingset_test_recent(void *shadow, bool file, bool *workingset);
 void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
 void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg);
 void workingset_refault(struct folio *folio, void *shadow);
diff --git a/mm/workingset.c b/mm/workingset.c
index 79585d55c45d..51ed8c836467 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -244,6 +244,30 @@  static void *lru_gen_eviction(struct folio *folio)
 	return pack_shadow(mem_cgroup_id(memcg), pgdat, token, refs);
 }
 
+/**
+ * Test if the folio is recently evicted.
+ *
+ * As a side effect, also populates the references with
+ * values unpacked from the shadow of the evicted folio.
+ */
+static bool lru_gen_test_recent(void *shadow, bool file, int *memcgid,
+	struct pglist_data **pgdat, unsigned long *token, bool *workingset)
+{
+	struct mem_cgroup *eviction_memcg;
+	struct lruvec *lruvec;
+	struct lru_gen_struct *lrugen;
+	unsigned long min_seq;
+
+	unpack_shadow(shadow, memcgid, pgdat, token, workingset);
+	eviction_memcg = mem_cgroup_from_id(*memcgid);
+
+	lruvec = mem_cgroup_lruvec(eviction_memcg, *pgdat);
+	lrugen = &lruvec->lrugen;
+
+	min_seq = READ_ONCE(lrugen->min_seq[file]);
+	return !((*token >> LRU_REFS_WIDTH) != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)));
+}
+
 static void lru_gen_refault(struct folio *folio, void *shadow)
 {
 	int hist, tier, refs;
@@ -258,23 +282,24 @@  static void lru_gen_refault(struct folio *folio, void *shadow)
 	int type = folio_is_file_lru(folio);
 	int delta = folio_nr_pages(folio);
 
-	unpack_shadow(shadow, &memcg_id, &pgdat, &token, &workingset);
-
-	if (pgdat != folio_pgdat(folio))
-		return;
 
 	rcu_read_lock();
 
 	memcg = folio_memcg_rcu(folio);
+
+	if (!lru_gen_test_recent(shadow, type, &memcg_id, &pgdat, &token,
+		&workingset))
+		goto unlock;
+
 	if (memcg_id != mem_cgroup_id(memcg))
 		goto unlock;
 
+	if (pgdat != folio_pgdat(folio))
+		goto unlock;
+
 	lruvec = mem_cgroup_lruvec(memcg, pgdat);
 	lrugen = &lruvec->lrugen;
-
 	min_seq = READ_ONCE(lrugen->min_seq[type]);
-	if ((token >> LRU_REFS_WIDTH) != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)))
-		goto unlock;
 
 	hist = lru_hist_from_seq(min_seq);
 	/* see the comment in folio_lru_refs() */
@@ -306,6 +331,12 @@  static void *lru_gen_eviction(struct folio *folio)
 	return NULL;
 }
 
+static bool lru_gen_test_recent(void *shadow, int type, int *memcgid,
+	struct pglist_data **pgdat, unsigned long *token, bool *workingset)
+{
+	return true;
+}
+
 static void lru_gen_refault(struct folio *folio, void *shadow)
 {
 }
@@ -374,39 +405,31 @@  void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg)
 }
 
 /**
- * workingset_refault - Evaluate the refault of a previously evicted folio.
- * @folio: The freshly allocated replacement folio.
- * @shadow: Shadow entry of the evicted folio.
+ * Test if the folio is recently evicted by checking if
+ * refault distance of shadow exceeds workingset size.
  *
- * Calculates and evaluates the refault distance of the previously
- * evicted folio in the context of the node and the memcg whose memory
- * pressure caused the eviction.
+ * As a side effect, populate workingset with the value
+ * unpacked from shadow.
  */
-void workingset_refault(struct folio *folio, void *shadow)
+bool workingset_test_recent(void *shadow, bool file, bool *workingset)
 {
-	bool file = folio_is_file_lru(folio);
 	struct mem_cgroup *eviction_memcg;
 	struct lruvec *eviction_lruvec;
 	unsigned long refault_distance;
 	unsigned long workingset_size;
-	struct pglist_data *pgdat;
-	struct mem_cgroup *memcg;
-	unsigned long eviction;
-	struct lruvec *lruvec;
 	unsigned long refault;
-	bool workingset;
+
 	int memcgid;
-	long nr;
+	struct pglist_data *pgdat;
+	unsigned long eviction;
 
-	if (lru_gen_enabled()) {
-		lru_gen_refault(folio, shadow);
-		return;
-	}
+	if (lru_gen_enabled())
+		return lru_gen_test_recent(shadow, file, &memcgid,
+			&pgdat, &eviction, workingset);
 
-	unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset);
+	unpack_shadow(shadow, &memcgid, &pgdat, &eviction, workingset);
 	eviction <<= bucket_order;
 
-	rcu_read_lock();
 	/*
 	 * Look up the memcg associated with the stored ID. It might
 	 * have been deleted since the folio's eviction.
@@ -425,7 +448,8 @@  void workingset_refault(struct folio *folio, void *shadow)
 	 */
 	eviction_memcg = mem_cgroup_from_id(memcgid);
 	if (!mem_cgroup_disabled() && !eviction_memcg)
-		goto out;
+		return false;
+
 	eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat);
 	refault = atomic_long_read(&eviction_lruvec->nonresident_age);
 
@@ -447,21 +471,6 @@  void workingset_refault(struct folio *folio, void *shadow)
 	 */
 	refault_distance = (refault - eviction) & EVICTION_MASK;
 
-	/*
-	 * The activation decision for this folio is made at the level
-	 * where the eviction occurred, as that is where the LRU order
-	 * during folio reclaim is being determined.
-	 *
-	 * However, the cgroup that will own the folio is the one that
-	 * is actually experiencing the refault event.
-	 */
-	nr = folio_nr_pages(folio);
-	memcg = folio_memcg(folio);
-	pgdat = folio_pgdat(folio);
-	lruvec = mem_cgroup_lruvec(memcg, pgdat);
-
-	mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
-
 	mem_cgroup_flush_stats_delayed();
 	/*
 	 * Compare the distance to the existing workingset size. We
@@ -483,8 +492,51 @@  void workingset_refault(struct folio *folio, void *shadow)
 						     NR_INACTIVE_ANON);
 		}
 	}
-	if (refault_distance > workingset_size)
+
+	return refault_distance <= workingset_size;
+}
+
+/**
+ * workingset_refault - Evaluate the refault of a previously evicted folio.
+ * @folio: The freshly allocated replacement folio.
+ * @shadow: Shadow entry of the evicted folio.
+ *
+ * Calculates and evaluates the refault distance of the previously
+ * evicted folio in the context of the node and the memcg whose memory
+ * pressure caused the eviction.
+ */
+void workingset_refault(struct folio *folio, void *shadow)
+{
+	bool file = folio_is_file_lru(folio);
+	struct pglist_data *pgdat;
+	struct mem_cgroup *memcg;
+	struct lruvec *lruvec;
+	bool workingset;
+	long nr;
+
+	if (lru_gen_enabled()) {
+		lru_gen_refault(folio, shadow);
+		return;
+	}
+
+	rcu_read_lock();
+
+	nr = folio_nr_pages(folio);
+	memcg = folio_memcg(folio);
+	pgdat = folio_pgdat(folio);
+	lruvec = mem_cgroup_lruvec(memcg, pgdat);
+
+	if (!workingset_test_recent(shadow, file, &workingset)) {
+		/*
+		 * The activation decision for this folio is made at the level
+		 * where the eviction occurred, as that is where the LRU order
+		 * during folio reclaim is being determined.
+		 *
+		 * However, the cgroup that will own the folio is the one that
+		 * is actually experiencing the refault event.
+		 */
 		goto out;
+	}
 
 	folio_set_active(folio);
 	workingset_age_nonresident(lruvec, nr);
@@ -498,6 +550,7 @@  void workingset_refault(struct folio *folio, void *shadow)
 		mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + file, nr);
 	}
 out:
+	mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
 	rcu_read_unlock();
 }