linux-kernel - Re: [PATCH v3] mm: memcontrol: add {pgscan,pgsteal}_{kswapd,direct} items in memory.stat of cgroup v2

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Date:   Mon, 6 Jun 2022 13:34:59 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Qi Zheng <zhengqi.arch@...edance.com>
Cc:     roman.gushchin@...ux.dev, shakeelb@...gle.com,
        songmuchun@...edance.com, mhocko@...nel.org,
        akpm@...ux-foundation.org, corbet@....net, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v3] mm: memcontrol: add {pgscan,pgsteal}_{kswapd,direct}
 items in memory.stat of cgroup v2

On Mon, Jun 06, 2022 at 11:40:28PM +0800, Qi Zheng wrote:
> There are already statistics of {pgscan,pgsteal}_kswapd and
> {pgscan,pgsteal}_direct of memcg event here, but now only the
> sum of the two is displayed in memory.stat of cgroup v2.
> 
> In order to obtain more accurate information during monitoring
> and debugging, and to align with the display in /proc/vmstat,
> it better to display {pgscan,pgsteal}_kswapd and
> {pgscan,pgsteal}_direct separately.
> 
> Also, for forward compatibility, we still display pgscan and
> pgsteal items so that it won't break existing applications.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
> Acked-by: Muchun Song <songmuchun@...edance.com>
> Acked-by: Shakeel Butt <shakeelb@...gle.com>
> Acked-by: Michal Hocko <mhocko@...e.com>

No objection to keeping pgscan and pgsteal, but can you please fix the
doc to present the items in the same order as memory.stat has them?

> @@ -1445,9 +1445,21 @@ PAGE_SIZE multiple when read back.
>  	  pgscan (npn)
>  		Amount of scanned pages (in an inactive LRU list)
>  
> +	  pgscan_kswapd (npn)
> +		Amount of scanned pages by kswapd (in an inactive LRU list)
> +
> +	  pgscan_direct (npn)
> +		Amount of scanned pages directly  (in an inactive LRU list)
> +
>  	  pgsteal (npn)
>  		Amount of reclaimed pages
>  
> +	  pgsteal_kswapd (npn)
> +		Amount of reclaimed pages by kswapd
> +
> +	  pgsteal_direct (npn)
> +		Amount of reclaimed pages directly
> +
>  	  pgactivate (npn)
>  		Amount of pages moved to the active LRU list

vs:

> @@ -1495,41 +1518,17 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
>  	}
>  
>  	/* Accumulated memory events */
> -
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGFAULT),
> -		       memcg_events(memcg, PGFAULT));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGMAJFAULT),
> -		       memcg_events(memcg, PGMAJFAULT));
> -	seq_buf_printf(&s, "%s %lu\n",  vm_event_name(PGREFILL),
> -		       memcg_events(memcg, PGREFILL));
>  	seq_buf_printf(&s, "pgscan %lu\n",
>  		       memcg_events(memcg, PGSCAN_KSWAPD) +
>  		       memcg_events(memcg, PGSCAN_DIRECT));
>  	seq_buf_printf(&s, "pgsteal %lu\n",
>  		       memcg_events(memcg, PGSTEAL_KSWAPD) +
>  		       memcg_events(memcg, PGSTEAL_DIRECT));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGACTIVATE),
> -		       memcg_events(memcg, PGACTIVATE));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGDEACTIVATE),
> -		       memcg_events(memcg, PGDEACTIVATE));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREE),
> -		       memcg_events(memcg, PGLAZYFREE));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREED),
> -		       memcg_events(memcg, PGLAZYFREED));
> -
> -#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(ZSWPIN),
> -		       memcg_events(memcg, ZSWPIN));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(ZSWPOUT),
> -		       memcg_events(memcg, ZSWPOUT));
> -#endif
>  
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_FAULT_ALLOC),
> -		       memcg_events(memcg, THP_FAULT_ALLOC));
> -	seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_COLLAPSE_ALLOC),
> -		       memcg_events(memcg, THP_COLLAPSE_ALLOC));
> -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> +	for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++)
> +		seq_buf_printf(&s, "%s %lu\n",
> +			       vm_event_name(memcg_vm_event_stat[i]),
> +			       memcg_events(memcg, memcg_vm_event_stat[i]));

Thanks