linux-kernel - RE:(2) [PATCH] f2fs: including waf data in f2fs status information

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Date:   Mon, 12 Jun 2023 16:52:50 +0900
From:   beomsu kim <beomsu7.kim@...sung.com>
To:     Chao Yu <chao@...nel.org>,
        "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yonggil Song <yonggil.song@...sung.com>,
        Seokhwan Kim <sukka.kim@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        Seonghun Kim <seonghun-sui.kim@...sung.com>
Subject: RE:(2) [PATCH] f2fs: including waf data in f2fs status information

On 2023/6/2 12:48, beomsu kim wrote:
>> When evaluating in f2fs, it takes much time to obtain waf data.
>> This patch helps to obtain waf data without calcluation.
>> 
>> Signed-off-by: Beomsu Kim <beomsu7.kim@...sung.com>
>> ---
>>   fs/f2fs/iostat.c | 16 ++++++++++++++++
>>   1 file changed, 16 insertions(+)
>> 
>> diff --git a/fs/f2fs/iostat.c b/fs/f2fs/iostat.c
>> index 3d5bfb1ad585..6eab11b0610d 100644
>> --- a/fs/f2fs/iostat.c
>> +++ b/fs/f2fs/iostat.c
>> @@ -34,10 +34,22 @@ int __maybe_unused iostat_info_seq_show(struct seq_file *seq, void *offset)
>>   {
>>          struct super_block *sb = seq->private;
>>          struct f2fs_sb_info *sbi = F2FS_SB(sb);
>> +       int j;
>> +       unsigned long long waf = 0;
>> +       unsigned long long data_written_to_storage = 0;
>> +       unsigned long long data_written_by_user = 0;
>>   
>>          if (!sbi->iostat_enable)
>>                  return 0;
>>   
>> +       for (j = FS_DATA_IO; j <= FS_CP_META_IO; j++)
>
>FS_CDATA_IO is redundant?

I agree, and modified it.
		
>
>> +               data_written_to_storage += sbi->iostat_bytes[j];
>> +       for (j = FS_DATA_IO; j <= FS_CDATA_IO; j++)
>
>Just needs to include APP_WRITE_IO and APP_MAPPED_IO?

There is a slight time interval between requests in the form of APP_*_IO until they become requests in the form of FS_*_IO. On the other hand, we get the amount of file system meta data from FS_*_IO for 'data_written_to_storage'. So, If we use APP_*_IO for 'data_written_by_user', the 'waf' value returned during this time interval might have some difference from the actual value.

>
>Thanks,
>
>> +               data_written_by_user += sbi->iostat_bytes[j];
>> +
>> +       if (data_written_by_user > 0)
>> +               waf = data_written_to_storage * 100 / data_written_by_user;
>> +
>>          seq_printf(seq, "time:          %-16llu\n>", ktime_get_real_seconds());
>>          seq_printf(seq, "\t\t\t%-16s %-16s %-16s\n>",
>>                                  "io_bytes", "count", "avg_bytes");
>> @@ -81,6 +93,10 @@ int __maybe_unused iostat_info_seq_show(struct seq_file *seq, void *offset)
>>          IOSTAT_INFO_SHOW("fs discard", FS_DISCARD_IO);
>>          IOSTAT_INFO_SHOW("fs flush", FS_FLUSH_IO);
>>   
>> +       /* print waf */
>> +       seq_puts(seq, "[WAF]\n>");
>> +       seq_printf(seq, "fs waf:                %llu.%02llu\n>", waf / 100, waf % 100);
>> +
>>          return 0;
>>   }
>>