Re: [PATCH RFC 2/5] f2fs: record average update time of segment

Chao Yu
2020-07-03T02:15:08Z

On 2020/7/2 0:19, Jaegeuk Kim wrote:
> On 06/30, Chao Yu wrote:
>> Previously, once we update one block in segment, we will update mtime of
>> segment to last time, making aged segment becoming freshest, result in
>> that GC with cost benefit algorithm missing such segment, So this patch
>> changes to record mtime as average block updating time instead of last
>> updating time.
>>
>> It's not needed to reset mtime for prefree segment, as se->valid_blocks
>> is zero, then old se->mtime won't take any weight with below calculation:
>>
>> se->mtime = (se->mtime * se->valid_blocks + mtime) /
>> (se->valid_blocks + 1);
>>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> ---
>> fs/f2fs/segment.c | 21 ++++++++++++++++++---
>> 1 file changed, 18 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 863ec6f1fb87..906c313835ad 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -2150,6 +2150,22 @@ static void __set_sit_entry_type(struct f2fs_sb_info *sbi, int type,
>> __mark_sit_entry_dirty(sbi, segno);
>> }
>>
>> +static void update_segment_mtime(struct f2fs_sb_info *sbi, block_t blkaddr)
>> +{
>> + unsigned int segno = GET_SEGNO(sbi, blkaddr);
>> + struct seg_entry *se = get_seg_entry(sbi, segno);
>> + unsigned long long mtime = get_mtime(sbi, false);
>> +
>> + if (!se->mtime) {
>
> Don't need {}.

Updated,

BTW, have fixed below compile error:

m68k-linux-ld: fs/f2fs/segment.o: in function `update_segment_mtime':
fs/f2fs/segment.c:2162: undefined reference to `__udivdi3'

Thanks,

>
>> + se->mtime = mtime;
>> + } else {
>> + se->mtime = (se->mtime * se->valid_blocks + mtime) /
>> + (se->valid_blocks + 1);
>> + }
>> + if (mtime > SIT_I(sbi)->max_mtime)
>> + SIT_I(sbi)->max_mtime = mtime;
>> +}
>> +
>> static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
>> {
>> struct seg_entry *se;
>> @@ -2169,10 +2185,9 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
>> f2fs_bug_on(sbi, (new_vblocks >> (sizeof(unsigned short) << 3) ||
>> (new_vblocks > sbi->blocks_per_seg)));
>>
>> + update_segment_mtime(sbi, blkaddr);
>> +
>> se->valid_blocks = new_vblocks;
>> - se->mtime = get_mtime(sbi, false);
>> - if (se->mtime > SIT_I(sbi)->max_mtime)
>> - SIT_I(sbi)->max_mtime = se->mtime;
>>
>> /* Update valid block bitmap */
>> if (del > 0) {
>> --
>> 2.26.2
> .
>