On Tue, Oct 17, 2023 at 4:21 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote:
>
> From: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
>
> 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 <nphamcs@xxxxxxxxx>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
> Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
> ---
> 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 },
zswap_writeback would be more consistent with file_writeback below.
Taking a step back, this is not really a "state". We increment it by 1
every time and never decrement it. Sounds awfully similar to events :)
You can also use count_objcg_event() directly and avoid the need for
obj_cgroup_report_zswap_wb() below.
> #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
