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Subject: Re: [PATCH] ext4: change the type of ext4 cache stats to
 percpu_counter to improve performance
To:     "Theodore Y. Ts'o" <tytso@mit.edu>, <linux-ext4@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Yang Guo <guoyang2@huawei.com>,
        "Andreas Dilger" <adilger.kernel@dilger.ca>
References: <1566528454-13725-1-git-send-email-zhangshaokun@hisilicon.com>
 <20190825032524.GD5163@mit.edu> <20190825172803.GA9505@sol.localdomain>
 <20190826004744.GA27472@mit.edu>
From:   Shaokun Zhang <zhangshaokun@hisilicon.com>
Message-ID: <f0495aa7-8f21-e938-9617-07ac8741acb7@hisilicon.com>
Date:   Mon, 26 Aug 2019 16:24:20 +0800
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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
> 
> .
>