• Jaegeuk Kim's avatar
    f2fs: add block_age-based extent cache · 71644dff
    Jaegeuk Kim authored
    This patch introduces a runtime hot/cold data separation method
    for f2fs, in order to improve the accuracy for data temperature
    classification, reduce the garbage collection overhead after
    long-term data updates.
    
    Enhanced hot/cold data separation can record data block update
    frequency as "age" of the extent per inode, and take use of the age
    info to indicate better temperature type for data block allocation:
     - It records total data blocks allocated since mount;
     - When file extent has been updated, it calculate the count of data
    blocks allocated since last update as the age of the extent;
     - Before the data block allocated, it searches for the age info and
    chooses the suitable segment for allocation.
    
    Test and result:
     - Prepare: create about 30000 files
      * 3% for cold files (with cold file extension like .apk, from 3M to 10M)
      * 50% for warm files (with random file extension like .FcDxq, from 1K
    to 4M)
      * 47% for hot files (with hot file extension like .db, from 1K to 256K)
     - create(5%)/random update(90%)/delete(5%) the files
      * total write amount is about 70G
      * fsync will be called for .db files, and buffered write will be used
    for other files
    
    The storage of test device is large enough(128G) so that it will not
    switch to SSR mode during the test.
    
    Benefit: dirty segment count increment reduce about 14%
     - before: Dirty +21110
     - after:  Dirty +18286
    Signed-off-by: default avatarqixiaoyu1 <qixiaoyu1@xiaomi.com>
    Signed-off-by: default avatarxiongping1 <xiongping1@xiaomi.com>
    Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
    71644dff
extent_cache.c 30.6 KB