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From:   Namjae Jeon <linkinjeon@kernel.org>
Date:   Tue, 8 Nov 2022 17:00:49 +0900
Message-ID: <CAKYAXd9JjNKvLKzFJKaZs5FOAVrL4dzsnzUC=JHYEn1j8jdZDw@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] exfat: hint the empty entry which at the end of
 cluster chain
To:     "Yuezhang.Mo@sony.com" <Yuezhang.Mo@sony.com>
Cc:     Sungjong Seo <sj1557.seo@samsung.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "Andy.Wu@sony.com" <Andy.Wu@sony.com>,
        "Wataru.Aoyama@sony.com" <Wataru.Aoyama@sony.com>
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2022-11-02 16:11 GMT+09:00, Yuezhang.Mo@sony.com <Yuezhang.Mo@sony.com>:
> After traversing all directory entries, hint the empty directory
> entry no matter whether or not there are enough empty directory
> entries.
>
> After this commit, hint the empty directory entries like this:
>
> 1. Hint the deleted directory entries if enough;
> 2. Hint the deleted and unused directory entries which at the
>    end of the cluster chain no matter whether enough or not(Add
>    by this commit);
> 3. If no any empty directory entries, hint the empty directory
>    entries in the new cluster(Add by this commit).
>
> This avoids repeated traversal of directory entries, reduces CPU
> usage, and improves the performance of creating files and
> directories(especially on low-performance CPUs).
>
> Test create 5000 files in a class 4 SD card on imx6q-sabrelite
> with:
>
> for ((i=0;i<5;i++)); do
>    sync
>    time (for ((j=1;j<=1000;j++)); do touch file$((i*1000+j)); done)
> done
>
> The more files, the more performance improvements.
>
>             Before   After    Improvement
>    1~1000   25.360s  22.168s  14.40%
> 1001~2000   38.242s  28.72ss  33.15%
> 2001~3000   49.134s  35.037s  40.23%
> 3001~4000   62.042s  41.624s  49.05%
> 4001~5000   73.629s  46.772s  57.42%
>
> Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
> Reviewed-by: Andy Wu <Andy.Wu@sony.com>
> Reviewed-by: Aoyama Wataru <wataru.aoyama@sony.com>
Applied. Thanks for your patch!