linux-ext4 - Re: [PATCH] ext4: change the type of ext4 cache stats to percpu

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Message-ID: <20190826004744.GA27472@mit.edu>
Date:   Sun, 25 Aug 2019 20:47:44 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Shaokun Zhang <zhangshaokun@...ilicon.com>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yang Guo <guoyang2@...wei.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>
Subject: Re: [PATCH] ext4: change the type of ext4 cache stats to
 percpu_counter to improve performance

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.

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,
but it's also wrong.

I've dropped this patch from the ext4 git tree.

     	     	  	     	      - Ted