Hello,
while expecting slow btrfs volumes i switched to kernel v4.13 and to
space_cache=v2.
But i'm still expecting slow performance and single kworker processes
using 100% CPU.
Tracing the kworker process shows me:
# sed 's/.*: //' /trace | sort | uniq -c | sort -n
21595 tree_search_offset.isra.23 <-btrfs_find_space_for_alloc
21610 btrfs_find_space_for_alloc <-find_free_extent
21619 _raw_spin_lock <-btrfs_find_space_for_alloc
27431 _cond_resched <-find_free_extent
27437 down_read <-find_free_extent
27451 block_group_cache_done.isra.29 <-find_free_extent
27451 btrfs_put_block_group <-find_free_extent
27464 up_read <-find_free_extent
27486 __get_raid_index <-find_free_extent
27503 _raw_spin_lock <-find_free_extent
48335 search_bitmap <-btrfs_find_space_for_alloc
Is there anything to optimize? Can i speed up this?
There's still plenty of unallocated space:
# btrfs fi usage /vmbackup/
Overall:
Device size: 58.20TiB
Device allocated: 22.66TiB
Device unallocated: 35.54TiB
Device missing: 0.00B
Used: 21.07TiB
Free (estimated): 37.12TiB (min: 37.12TiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 512.00MiB (used: 0.00B)
Data,RAID0: Size:22.57TiB, Used:20.99TiB
/dev/sdc1 5.64TiB
/dev/sdd1 5.64TiB
/dev/sde1 5.64TiB
/dev/sdf1 5.64TiB
Metadata,RAID0: Size:90.00GiB, Used:81.60GiB
/dev/sdc1 22.50GiB
/dev/sdd1 22.50GiB
/dev/sde1 22.50GiB
/dev/sdf1 22.50GiB
System,RAID0: Size:64.00MiB, Used:1.53MiB
/dev/sdc1 16.00MiB
/dev/sdd1 16.00MiB
/dev/sde1 16.00MiB
/dev/sdf1 16.00MiB
Unallocated:
/dev/sdc1 8.88TiB
/dev/sdd1 8.88TiB
/dev/sde1 8.88TiB
/dev/sdf1 8.88TiB
Is btrfs trying to hard to find free space?
Greets,
Stefan
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