• Miao Xie's avatar
    Btrfs: reclaim the reserved metadata space at background · 21c7e756
    Miao Xie authored
    Before applying this patch, the task had to reclaim the metadata space
    by itself if the metadata space was not enough. And When the task started
    the space reclamation, all the other tasks which wanted to reserve the
    metadata space were blocked. At some cases, they would be blocked for
    a long time, it made the performance fluctuate wildly.
    
    So we introduce the background metadata space reclamation, when the space
    is about to be exhausted, we insert a reclaim work into the workqueue, the
    worker of the workqueue helps us to reclaim the reserved space at the
    background. By this way, the tasks needn't reclaim the space by themselves at
    most cases, and even if the tasks have to reclaim the space or are blocked
    for the space reclamation, they will get enough space more quickly.
    
    Here is my test result(Tested by compilebench):
     Memory:	2GB
     CPU:		2Cores * 1CPU
     Partition:	40GB(SSD)
    
    Test command:
     # compilebench -D <mnt> -m
    
    Without this patch:
     intial create total runs 30 avg 54.36 MB/s (user 0.52s sys 2.44s)
     compile total runs 30 avg 123.72 MB/s (user 0.13s sys 1.17s)
     read compiled tree total runs 3 avg 81.15 MB/s (user 0.74s sys 4.89s)
     delete compiled tree total runs 30 avg 5.32 seconds (user 0.35s sys 4.37s)
    
    With this patch:
     intial create total runs 30 avg 59.80 MB/s (user 0.52s sys 2.53s)
     compile total runs 30 avg 151.44 MB/s (user 0.13s sys 1.11s)
     read compiled tree total runs 3 avg 83.25 MB/s (user 0.76s sys 4.91s)
     delete compiled tree total runs 30 avg 5.29 seconds (user 0.34s sys 4.34s)
    Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
    Signed-off-by: default avatarChris Mason <clm@fb.com>
    21c7e756
super.c 51.9 KB