memcg: reduce memory for the lruvec and memcg stats

At the moment, the amount of memory allocated for stats related structs in
the mem_cgroup corresponds to the size of enum node_stat_item.  However
not all fields in enum node_stat_item have corresponding memcg stats.  So,
let's use indirection mechanism similar to the one used for memcg vmstats
management.

For a given x86_64 config, the size of stats with and without patch is:

structs size in bytes         w/o     with

struct lruvec_stats           1128     648
struct lruvec_stats_percpu     752     432
struct memcg_vmstats          1832    1352
struct memcg_vmstats_percpu   1280     960

The memory savings are further compounded by the fact that these structs
are allocated for each cpu and for each node.  To be precise, for each
memcg the memory saved would be:

Memory saved = ((21 * 3 * NR_NODES) + (21 * 2 * NR_NODES * NR_CPUS) +
	       (21 * 3) + (21 * 2 * NR_CPUS)) * sizeof(long)

Where 21 is the number of fields eliminated.

Link: https://lkml.kernel.org/r/20240501172617.678560-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: T.J. Mercier <tjmercier@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 42e0062d880b7fb742faf56663addac0e8e0e2ae..0dad17d26ce2c678c1859812b732ce69aa111c94 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -575,35 +575,106 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
        return mz;
 }
 
+/* Subset of node_stat_item for memcg stats */
+static const unsigned int memcg_node_stat_items[] = {
+       NR_INACTIVE_ANON,
+       NR_ACTIVE_ANON,
+       NR_INACTIVE_FILE,
+       NR_ACTIVE_FILE,
+       NR_UNEVICTABLE,
+       NR_SLAB_RECLAIMABLE_B,
+       NR_SLAB_UNRECLAIMABLE_B,
+       WORKINGSET_REFAULT_ANON,
+       WORKINGSET_REFAULT_FILE,
+       WORKINGSET_ACTIVATE_ANON,
+       WORKINGSET_ACTIVATE_FILE,
+       WORKINGSET_RESTORE_ANON,
+       WORKINGSET_RESTORE_FILE,
+       WORKINGSET_NODERECLAIM,
+       NR_ANON_MAPPED,
+       NR_FILE_MAPPED,
+       NR_FILE_PAGES,
+       NR_FILE_DIRTY,
+       NR_WRITEBACK,
+       NR_SHMEM,
+       NR_SHMEM_THPS,
+       NR_FILE_THPS,
+       NR_ANON_THPS,
+       NR_KERNEL_STACK_KB,
+       NR_PAGETABLE,
+       NR_SECONDARY_PAGETABLE,
+#ifdef CONFIG_SWAP
+       NR_SWAPCACHE,
+#endif
+};
+
+static const unsigned int memcg_stat_items[] = {
+       MEMCG_SWAP,
+       MEMCG_SOCK,
+       MEMCG_PERCPU_B,
+       MEMCG_VMALLOC,
+       MEMCG_KMEM,
+       MEMCG_ZSWAP_B,
+       MEMCG_ZSWAPPED,
+};
+
+#define NR_MEMCG_NODE_STAT_ITEMS ARRAY_SIZE(memcg_node_stat_items)
+#define MEMCG_VMSTAT_SIZE (NR_MEMCG_NODE_STAT_ITEMS + \
+                          ARRAY_SIZE(memcg_stat_items))
+static int8_t mem_cgroup_stats_index[MEMCG_NR_STAT] __read_mostly;
+
+static void init_memcg_stats(void)
+{
+       int8_t i, j = 0;
+
+       BUILD_BUG_ON(MEMCG_NR_STAT >= S8_MAX);
+
+       for (i = 0; i < NR_MEMCG_NODE_STAT_ITEMS; ++i)
+               mem_cgroup_stats_index[memcg_node_stat_items[i]] = ++j;
+
+       for (i = 0; i < ARRAY_SIZE(memcg_stat_items); ++i)
+               mem_cgroup_stats_index[memcg_stat_items[i]] = ++j;
+}
+
+static inline int memcg_stats_index(int idx)
+{
+       return mem_cgroup_stats_index[idx] - 1;
+}
+
 struct lruvec_stats_percpu {
        /* Local (CPU and cgroup) state */
-       long state[NR_VM_NODE_STAT_ITEMS];
+       long state[NR_MEMCG_NODE_STAT_ITEMS];
 
        /* Delta calculation for lockless upward propagation */
-       long state_prev[NR_VM_NODE_STAT_ITEMS];
+       long state_prev[NR_MEMCG_NODE_STAT_ITEMS];
 };
 
 struct lruvec_stats {
        /* Aggregated (CPU and subtree) state */
-       long state[NR_VM_NODE_STAT_ITEMS];
+       long state[NR_MEMCG_NODE_STAT_ITEMS];
 
        /* Non-hierarchical (CPU aggregated) state */
-       long state_local[NR_VM_NODE_STAT_ITEMS];
+       long state_local[NR_MEMCG_NODE_STAT_ITEMS];
 
        /* Pending child counts during tree propagation */
-       long state_pending[NR_VM_NODE_STAT_ITEMS];
+       long state_pending[NR_MEMCG_NODE_STAT_ITEMS];
 };
 
 unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
 {
        struct mem_cgroup_per_node *pn;
        long x;
+       int i;
 
        if (mem_cgroup_disabled())
                return node_page_state(lruvec_pgdat(lruvec), idx);
 
+       i = memcg_stats_index(idx);
+       if (i < 0)
+               return 0;
+
        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
-       x = READ_ONCE(pn->lruvec_stats->state[idx]);
+       x = READ_ONCE(pn->lruvec_stats->state[i]);
 #ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
@@ -616,12 +687,17 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec,
 {
        struct mem_cgroup_per_node *pn;
        long x = 0;
+       int i;
 
        if (mem_cgroup_disabled())
                return node_page_state(lruvec_pgdat(lruvec), idx);
 
+       i = memcg_stats_index(idx);
+       if (i < 0)
+               return 0;
+
        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
-       x = READ_ONCE(pn->lruvec_stats->state_local[idx]);
+       x = READ_ONCE(pn->lruvec_stats->state_local[i]);
 #ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
@@ -688,11 +764,11 @@ struct memcg_vmstats_percpu {
        /* The above should fit a single cacheline for memcg_rstat_updated() */
 
        /* Local (CPU and cgroup) page state & events */
-       long                    state[MEMCG_NR_STAT];
+       long                    state[MEMCG_VMSTAT_SIZE];
        unsigned long           events[NR_MEMCG_EVENTS];
 
        /* Delta calculation for lockless upward propagation */
-       long                    state_prev[MEMCG_NR_STAT];
+       long                    state_prev[MEMCG_VMSTAT_SIZE];
        unsigned long           events_prev[NR_MEMCG_EVENTS];
 
        /* Cgroup1: threshold notifications & softlimit tree updates */
@@ -702,15 +778,15 @@ struct memcg_vmstats_percpu {
 
 struct memcg_vmstats {
        /* Aggregated (CPU and subtree) page state & events */
-       long                    state[MEMCG_NR_STAT];
+       long                    state[MEMCG_VMSTAT_SIZE];
        unsigned long           events[NR_MEMCG_EVENTS];
 
        /* Non-hierarchical (CPU aggregated) page state & events */
-       long                    state_local[MEMCG_NR_STAT];
+       long                    state_local[MEMCG_VMSTAT_SIZE];
        unsigned long           events_local[NR_MEMCG_EVENTS];
 
        /* Pending child counts during tree propagation */
-       long                    state_pending[MEMCG_NR_STAT];
+       long                    state_pending[MEMCG_VMSTAT_SIZE];
        unsigned long           events_pending[NR_MEMCG_EVENTS];
 
        /* Stats updates since the last flush */
@@ -843,7 +919,13 @@ static void flush_memcg_stats_dwork(struct work_struct *w)
 
 unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
 {
-       long x = READ_ONCE(memcg->vmstats->state[idx]);
+       long x;
+       int i = memcg_stats_index(idx);
+
+       if (i < 0)
+               return 0;
+
+       x = READ_ONCE(memcg->vmstats->state[i]);
 #ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
@@ -875,18 +957,25 @@ static int memcg_state_val_in_pages(int idx, int val)
  */
 void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val)
 {
-       if (mem_cgroup_disabled())
+       int i = memcg_stats_index(idx);
+
+       if (mem_cgroup_disabled() || i < 0)
                return;
 
-       __this_cpu_add(memcg->vmstats_percpu->state[idx], val);
+       __this_cpu_add(memcg->vmstats_percpu->state[i], val);
        memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val));
 }
 
 /* idx can be of type enum memcg_stat_item or node_stat_item. */
 static unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
 {
-       long x = READ_ONCE(memcg->vmstats->state_local[idx]);
+       long x;
+       int i = memcg_stats_index(idx);
+
+       if (i < 0)
+               return 0;
 
+       x = READ_ONCE(memcg->vmstats->state_local[i]);
 #ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
@@ -900,6 +989,10 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
 {
        struct mem_cgroup_per_node *pn;
        struct mem_cgroup *memcg;
+       int i = memcg_stats_index(idx);
+
+       if (i < 0)
+               return;
 
        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
        memcg = pn->memcg;
@@ -926,10 +1019,10 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
        }
 
        /* Update memcg */
-       __this_cpu_add(memcg->vmstats_percpu->state[idx], val);
+       __this_cpu_add(memcg->vmstats_percpu->state[i], val);
 
        /* Update lruvec */
-       __this_cpu_add(pn->lruvec_stats_percpu->state[idx], val);
+       __this_cpu_add(pn->lruvec_stats_percpu->state[i], val);
 
        memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val));
        memcg_stats_unlock();
@@ -5697,6 +5790,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
                page_counter_init(&memcg->kmem, &parent->kmem);
                page_counter_init(&memcg->tcpmem, &parent->tcpmem);
        } else {
+               init_memcg_stats();
                init_memcg_events();
                page_counter_init(&memcg->memory, NULL);
                page_counter_init(&memcg->swap, NULL);
@@ -5868,7 +5962,7 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 
        statc = per_cpu_ptr(memcg->vmstats_percpu, cpu);
 
-       for (i = 0; i < MEMCG_NR_STAT; i++) {
+       for (i = 0; i < MEMCG_VMSTAT_SIZE; i++) {
                /*
                 * Collect the aggregated propagation counts of groups
                 * below us. We're in a per-cpu loop here and this is
@@ -5932,7 +6026,7 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 
                lstatc = per_cpu_ptr(pn->lruvec_stats_percpu, cpu);
 
-               for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
+               for (i = 0; i < NR_MEMCG_NODE_STAT_ITEMS; i++) {
                        delta = lstats->state_pending[i];
                        if (delta)
                                lstats->state_pending[i] = 0;