Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [RFC NO MERGE] f2fs: extent cache: support unaligned extent
To:     jaegeuk@kernel.org
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Chao Yu <chao.yu@linux.dev>
References: <20210707015815.1978-1-chao@kernel.org>
From:   Chao Yu <chao@kernel.org>
Message-ID: <ac39c9af-2ddd-5033-2b64-cb10aadc66a2@kernel.org>
Date:   Wed, 14 Jul 2021 10:27:21 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <20210707015815.1978-1-chao@kernel.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2021/7/7 9:58, Chao Yu wrote:
> Compressed inode may suffer read performance issue due to it can not
> use extent cache, so I propose to add this unaligned extent support
> to improve it.
> 
> Currently, it only works in readonly format f2fs image.
> 
> Unaligned extent: in one compressed cluster, physical block number
> will be less than logical block number, so we add an extra physical
> block length in extent info in order to indicate such extent status.
> 
> The idea is if one whole cluster blocks are contiguous physically,
> once its mapping info was readed at first time, we will cache an
> unaligned (or aligned) extent info entry in extent cache, it expects
> that the mapping info will be hitted when rereading cluster.
> 
> Merge policy:
> - Aligned extents can be merged.
> - Aligned extent and unaligned extent can not be merged.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
> 
> I just post this for comments, it passes compiling, w/o any test.
> 
>   fs/f2fs/compress.c     | 25 ++++++++++++
>   fs/f2fs/data.c         | 38 +++++++++++++-----
>   fs/f2fs/extent_cache.c | 90 +++++++++++++++++++++++++++++++++++++-----
>   fs/f2fs/f2fs.h         | 33 +++++++++++++---
>   fs/f2fs/node.c         | 20 ++++++++++
>   5 files changed, 181 insertions(+), 25 deletions(-)

Jaegeuk, any thoughts about this idea?

Thanks,