[PATCH v8 4/6] 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/vm_event_item.h | 1 +
 mm/memcontrol.c               | 1 +
 mm/vmstat.c                   | 1 +
 mm/zswap.c                    | 4 ++++
 4 files changed, 7 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index d1b847502f09..f4569ad98edf 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -142,6 +142,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_ZSWAP
                ZSWPIN,
                ZSWPOUT,
+               ZSWP_WB,
 #endif
 #ifdef CONFIG_X86
                DIRECT_MAP_LEVEL2_SPLIT,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 792ca21c5815..21d79249c8b4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -703,6 +703,7 @@ static const unsigned int memcg_vm_event_stat[] = {
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
        ZSWPIN,
        ZSWPOUT,
+       ZSWP_WB,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
        THP_FAULT_ALLOC,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index afa5a38fcc9c..2249f85e4a87 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1401,6 +1401,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_ZSWAP
        "zswpin",
        "zswpout",
+       "zswp_wb",
 #endif
 #ifdef CONFIG_X86
        "direct_map_level2_splits",
diff --git a/mm/zswap.c b/mm/zswap.c
index f323e45cbdc7..49b79393e472 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -760,6 +760,10 @@ static enum lru_status shrink_memcg_cb(struct list_head 
*item, struct list_lru_o
        }
        zswap_written_back_pages++;
 
+       if (entry->objcg)
+               count_objcg_event(entry->objcg, ZSWP_WB);
+
+       count_vm_event(ZSWP_WB);
        /*
         * Writeback started successfully, the page now belongs to the
         * swapcache. Drop the entry from zswap - unless invalidate already
-- 
2.34.1