[PATCH v3 3/5] mm: memcg: add per-memcg zswap writeback stat

[Nhat Pham]

From: Domenico Cerasuolo <cerasuolodomen...@gmail.com>

Since zswap now writes back pages from memcg-specific LRUs, we now need a
new stat to show writebacks count for each memcg.

Suggested-by: Nhat Pham <npha...@gmail.com>
Signed-off-by: Domenico Cerasuolo <cerasuolodomen...@gmail.com>
Signed-off-by: Nhat Pham <npha...@gmail.com>
---
 include/linux/memcontrol.h |  2 ++
 mm/memcontrol.c            | 15 +++++++++++++++
 mm/zswap.c                 |  3 +++
 3 files changed, 20 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3de10fabea0f..7868b1e00bf5 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -38,6 +38,7 @@ enum memcg_stat_item {
        MEMCG_KMEM,
        MEMCG_ZSWAP_B,
        MEMCG_ZSWAPPED,
+       MEMCG_ZSWAP_WB,
        MEMCG_NR_STAT,
 };
 
@@ -1884,6 +1885,7 @@ static inline void count_objcg_event(struct obj_cgroup 
*objcg,
 bool obj_cgroup_may_zswap(struct obj_cgroup *objcg);
 void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size);
 void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, size_t size);
+void obj_cgroup_report_zswap_wb(struct obj_cgroup *objcg);
 #else
 static inline bool obj_cgroup_may_zswap(struct obj_cgroup *objcg)
 {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1bde67b29287..a9118871e5a6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1505,6 +1505,7 @@ static const struct memory_stat memory_stats[] = {
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
        { "zswap",                      MEMCG_ZSWAP_B                   },
        { "zswapped",                   MEMCG_ZSWAPPED                  },
+       { "zswap_wb",                   MEMCG_ZSWAP_WB                  },
 #endif
        { "file_mapped",                NR_FILE_MAPPED                  },
        { "file_dirty",                 NR_FILE_DIRTY                   },
@@ -1541,6 +1542,7 @@ static int memcg_page_state_unit(int item)
        switch (item) {
        case MEMCG_PERCPU_B:
        case MEMCG_ZSWAP_B:
+       case MEMCG_ZSWAP_WB:
        case NR_SLAB_RECLAIMABLE_B:
        case NR_SLAB_UNRECLAIMABLE_B:
        case WORKINGSET_REFAULT_ANON:
@@ -7861,6 +7863,19 @@ void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, 
size_t size)
        rcu_read_unlock();
 }
 
+void obj_cgroup_report_zswap_wb(struct obj_cgroup *objcg)
+{
+       struct mem_cgroup *memcg;
+
+       if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+               return;
+
+       rcu_read_lock();
+       memcg = obj_cgroup_memcg(objcg);
+       mod_memcg_state(memcg, MEMCG_ZSWAP_WB, 1);
+       rcu_read_unlock();
+}
+
 static u64 zswap_current_read(struct cgroup_subsys_state *css,
                              struct cftype *cft)
 {
diff --git a/mm/zswap.c b/mm/zswap.c
index d2989ad11814..15485427e3fa 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -704,6 +704,9 @@ static enum lru_status shrink_memcg_cb(struct list_head 
*item, struct list_lru_o
        }
        zswap_written_back_pages++;
 
+       if (entry->objcg)
+               obj_cgroup_report_zswap_wb(entry->objcg);
+
        /*
         * Writeback started successfully, the page now belongs to the
         * swapcache. Drop the entry from zswap - unless invalidate already
-- 
2.34.1