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

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Date:   Tue, 7 Jun 2022 10:18:33 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     Johannes Weiner <hannes@...xchg.org>
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 2022/6/7 1:34 AM, Johannes Weiner wrote:
> 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?

Sure, will fix.

Thanks,
Qi

> 
>> @@ -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

-- 
Thanks,
Qi