linux-kernel - Re: [RFC NO MERGE] f2fs: extent cache: support unaligned extent

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Date:   Wed, 14 Jul 2021 10:27:21 +0800
From:   Chao Yu <chao@...nel.org>
To:     jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <chao.yu@...ux.dev>
Subject: Re: [RFC NO MERGE] f2fs: extent cache: support unaligned extent

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@...nel.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,