linux-kernel - Re: [PATCH] f2fs: compress: don't force buffered io when in COMPR_MODE

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Message-ID: <dde6972a-e98c-8a6e-493b-9aff5668101d@vivo.com>
Date:   Tue, 13 Jun 2023 12:14:22 +0800
From:   Yangtao Li <frank.li@...o.com>
To:     Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Qi Han <hanqi@...o.com>, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: compress: don't force buffered io when in
 COMPR_MODE_USER mode


On 2023/6/12 22:38, Chao Yu wrote:
> On 2023/6/9 21:15, Yangtao Li wrote:
>> It is observed that when in user compression mode 
>> (compress_extension=*),
>> even though the file is not compressed, the file is still forced to use
>> buffer io, which makes the AndroBench sequential read and write drop
>> significantly. In fact, when the file is not compressed, we don't need
>> to force it to buffer io.
>>
>>                   | w/o patch | w/ patch |
>> seq read  (MB/s) | 1320.068  | 3696.154 |
>> seq write (MB/s) | 617.996   | 2978.478 |
>>
>> Fixes: 4c8ff7095bef ("f2fs: support data compression")
>> Signed-off-by: Qi Han <hanqi@...o.com>
>> Signed-off-by: Yangtao Li <frank.li@...o.com>
>> ---
>>   fs/f2fs/f2fs.h | 14 ++++++++++++++
>>   fs/f2fs/file.c |  2 +-
>>   2 files changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 1efcfd9e5a99..7f5472525310 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -3168,6 +3168,20 @@ static inline int f2fs_compressed_file(struct 
>> inode *inode)
>>           is_inode_flag_set(inode, FI_COMPRESSED_FILE);
>>   }
>>   +static inline bool f2fs_is_compressed_file(struct inode *inode)
>> +{
>> +    int compress_mode = F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
>> +
>> +    if (compress_mode == COMPR_MODE_FS)
>> +        return f2fs_compressed_file(inode);
>> +    else if (atomic_read(&F2FS_I(inode)->i_compr_blocks) ||
>
> Should check dirty page as well? i_compr_blocks may increase after
> data writeback.
>
IIUC, in COMPR_MODE_USER mode, i_compr_blocks will only be updated when 
FI_ENABLE_COMPRESS is enabled.

If FI_ENABLE_COMPRESS is not enabled, i_compr_blocks will never be 
updated after data writeback.

So there is no need to additionally judge whether there is a dirty page?


Thanks,

> Thanks,
>
>> +        is_inode_flag_set(inode, FI_COMPRESS_RELEASED) ||
>> +        is_inode_flag_set(inode, FI_ENABLE_COMPRESS))
>> +        return true;
>> +
>> +    return false;
>> +}
>> +
>>   static inline bool f2fs_need_compress_data(struct inode *inode)
>>   {
>>       int compress_mode = F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 74ecc9e20619..0698129b2165 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -821,7 +821,7 @@ static bool f2fs_force_buffered_io(struct inode 
>> *inode, int rw)
>>           return true;
>>       if (fsverity_active(inode))
>>           return true;
>> -    if (f2fs_compressed_file(inode))
>> +    if (f2fs_is_compressed_file(inode))
>>           return true;
>>         /* disallow direct IO if any of devices has unaligned blksize */