Re: [PATCH] ext4: change the type of ext4 cache stats to percpu_counter to improve performance

[Shaokun Zhang]

Hi Ted,

On 2019/8/26 8:47, Theodore Y. Ts'o wrote:
> On Sun, Aug 25, 2019 at 10:28:03AM -0700, Eric Biggers wrote:
>> This patch is causing the following.  Probably because there's no calls to
>> percpu_counter_destroy() for the new counters?
> 
> Yeah, I noticed this from my test runs last night as well.  It looks
> like original patch was never tested with CONFIG_HOTPLUG_CPU.
> 

Sorry that We may miss it completely, we shall double check it and
make the proper patch carefully.

> The other problem with this patch is that it initializes
> es_stats_cache_hits and es_stats_cache_miesses too late.  They will
> get used when the journal inode is loaded.  This is mostly harmless,

I have checked it again, @es_stats_cache_hits and @es_stats_cache_miesses
have been initialized before the journal inode is loaded, Maybe I miss
something else?

egrep "ext4_es_register_shrinker|ext4_load_journal" fs/ext4/super.c
4260:   if (ext4_es_register_shrinker(sbi))
4302:           err = ext4_load_journal(sb, es, journal_devnum);

Thanks,
Shaokun

> but it's also wrong.
> 
> I've dropped this patch from the ext4 git tree.
> 
>      	     	  	     	      - Ted
> 
> .
>