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Subject: Re: [PATCH v2] f2fs: change write_hint for hot/warm nodes
To:     <daejun7.park@samsung.com>,
        "jaegeuk@kernel.org" <jaegeuk@kernel.org>,
        "chao@kernel.org" <chao@kernel.org>
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        yongmyung lee <ymhungry.lee@samsung.com>,
        Jieon Seol <jieon.seol@samsung.com>,
        Sang-yoon Oh <sangyoon.oh@samsung.com>,
        Mankyu PARK <manq.park@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        Keoseong Park <keosung.park@samsung.com>,
        SEUNGUK SHIN <seunguk.shin@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Jaemyung Lee <jaemyung.lee@samsung.com>
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From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <c885ff38-fce2-43d2-cfe1-57e0a3a0b449@huawei.com>
Date:   Tue, 3 Nov 2020 17:01:36 +0800
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On 2020/11/3 16:38, Daejun Park wrote:
> In the fs-based mode of F2FS, the mapping of hot/warm node to
> WRITE_LIFE_NOT_SET should be changed to WRITE_LIFE_SHORT.
> 
> As a result of analyzing the write pattern of f2fs using real workload,
> hot/warm nodes have high update ratio close to hot data.[*]
> However, F2FS passes write hints for hot/warm nodes as WRITE_LIFE_NOT_SET.
> 
> Furthermore, WRITE_LIFE_NOT_SET is a default value of write hint when it is
> not provided from the file system.
> In storage, write_hint is used to distinguish streams (e.g. NVMe).
> So, the hot/warm node of F2FS is not distinguished from other write_hints,
> which can make the wrong stream seperation.
> 
> * Liang, Yu, et al. "An empirical study of F2FS on mobile devices." 2017
> IEEE 23rd International Conference on Embedded and Real-Time Computing
> Systems and Applications (RTCSA).
> 
> Signed-off-by: Daejun Park <daejun7.park@samsung.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,