Re: [PATCH v4 2/4] mm: memcg: add a helper for non-unified stats flushing

Michal Hocko
2023-09-04T14:45:14Z

On Thu 31-08-23 16:56:09, Yosry Ahmed wrote:
> Some contexts flush memcg stats outside of unified flushing, directly
> using cgroup_rstat_flush(). Add a helper for non-unified flushing, a
> counterpart for do_unified_stats_flush(), and use it in those contexts,
> as well as in do_unified_stats_flush() itself.
>
> This abstracts the rstat API and makes it easy to introduce
> modifications to either unified or non-unified flushing functions
> without changing callers.
>
> No functional change intended.
>
> Signed-off-by: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>

> ---
> mm/memcontrol.c | 21 +++++++++++++++++----
> 1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2d0ec828a1c4..8c046feeaae7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -639,6 +639,17 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
> }
> }
>
> +/*
> + * do_stats_flush - do a flush of the memory cgroup statistics
> + * @memcg: memory cgroup to flush
> + *
> + * Only flushes the subtree of @memcg, does not skip under any conditions.
> + */
> +static void do_stats_flush(struct mem_cgroup *memcg)
> +{
> + cgroup_rstat_flush(memcg->css.cgroup);
> +}
> +
> /*
> * do_unified_stats_flush - do a unified flush of memory cgroup statistics
> *
> @@ -656,7 +667,7 @@ static void do_unified_stats_flush(void)
>
> WRITE_ONCE(flush_next_time, jiffies_64 + 2*FLUSH_TIME);
>
> - cgroup_rstat_flush(root_mem_cgroup->css.cgroup);
> + do_stats_flush(root_mem_cgroup);
>
> atomic_set(&stats_flush_threshold, 0);
> atomic_set(&stats_unified_flush_ongoing, 0);
> @@ -7790,7 +7801,7 @@ bool obj_cgroup_may_zswap(struct obj_cgroup *objcg)
> break;
> }
>
> - cgroup_rstat_flush(memcg->css.cgroup);
> + do_stats_flush(memcg);
> pages = memcg_page_state(memcg, MEMCG_ZSWAP_B) / PAGE_SIZE;
> if (pages < max)
> continue;
> @@ -7855,8 +7866,10 @@ void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, size_t size)
> static u64 zswap_current_read(struct cgroup_subsys_state *css,
> struct cftype *cft)
> {
> - cgroup_rstat_flush(css->cgroup);
> - return memcg_page_state(mem_cgroup_from_css(css), MEMCG_ZSWAP_B);
> + struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> +
> + do_stats_flush(memcg);
> + return memcg_page_state(memcg, MEMCG_ZSWAP_B);
> }
>
> static int zswap_max_show(struct seq_file *m, void *v)
> --
> 2.42.0.rc2.253.gd59a3bf2b4-goog

--
Michal Hocko
SUSE Labs