linux-kernel - Re: [PATCH v4] f2fs: readahead node blocks in F2FS_GET_BLOCK

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Message-ID: <6529ffee-d2ee-41ff-97d0-bf483fd0530a@kernel.org>
Date: Wed, 24 Sep 2025 15:58:58 +0800
From: Chao Yu <chao@...nel.org>
To: Yunji Kang <yunji0.kang@...sung.com>, jaegeuk@...nel.org
Cc: chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org, Sungjong Seo <sj1557.seo@...sung.com>,
 Sunmin Jeong <s_min.jeong@...sung.com>
Subject: Re: [PATCH v4] f2fs: readahead node blocks in F2FS_GET_BLOCK_PRECACHE
 mode

On 9/24/25 15:43, Yunji Kang wrote:
> In f2fs_precache_extents(), For large files, It requires reading many
> node blocks. Instead of reading each node block with synchronous I/O,
> this patch applies readahead so that node blocks can be fetched in
> advance.
> 
> It reduces the overhead of repeated sync reads and improves efficiency
> when precaching extents of large files.
> 
> I created a file with the same largest extent and executed the test.
> For this experiment, I set the file's largest extent with an offset of 0
> and a size of 1GB. I configured the remaining area with 100MB extents.
> 
> 5GB test file:
> dd if=/dev/urandom of=test1 bs=1m count=5120
> cp test1 test2
> fsync test1
> dd if=test1 of=test2 bs=1m skip=1024 seek=1024 count=100 conv=notrunc
> dd if=test1 of=test2 bs=1m skip=1224 seek=1224 count=100 conv=notrunc
> ...
> dd if=test1 of=test2 bs=1m skip=5024 seek=5024 count=100 conv=notrunc
> reboot
> 
> I also created 10GB and 20GB files with large extents using the same
> method.
> 
> ioctl(F2FS_IOC_PRECACHE_EXTENTS) test results are as follows:
>   +-----------+---------+---------+-----------+
>   | File size | Before  | After   | Reduction |
>   +-----------+---------+---------+-----------+
>   | 5GB       | 101.8ms | 37.0ms  | 72.1%     |
>   | 10GB      | 222.9ms | 56.0ms  | 74.9%     |
>   | 20GB      | 446.2ms | 116.4ms | 73.9%     |
>   +-----------+---------+---------+-----------+
> Tested on a 256GB mobile device with an SM8750 chipset.
> 
> Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>
> Reviewed-by: Sunmin Jeong <s_min.jeong@...sung.com>
> Signed-off-by: Yunji Kang <yunji0.kang@...sung.com>

Reviewed-by: Chao Yu <chao@...nel.org>

Thanks,