On 2018-11-22 21:46, Nikolay Borisov wrote:
# echo w > /proc/sysrq-trigger
# dmesg -c
[ 931.585611] sysrq: SysRq : Show Blocked State
[ 931.585715] task PC stack pid father
[ 931.590168] btrfs-cleaner D 0 1340 2 0x80000000
[ 931.590175] Call Trace:
[ 931.590190] __schedule+0x29e/0x840
[ 931.590195] schedule+0x2c/0x80
[ 931.590199] schedule_timeout+0x258/0x360
[ 931.590204] io_schedule_timeout+0x1e/0x50
[ 931.590208] wait_for_completion_io+0xb7/0x140
[ 931.590214] ? wake_up_q+0x80/0x80
[ 931.590219] submit_bio_wait+0x61/0x90
[ 931.590225] blkdev_issue_discard+0x7a/0xd0
[ 931.590266] btrfs_issue_discard+0x123/0x160 [btrfs]
[ 931.590299] btrfs_discard_extent+0xd8/0x160 [btrfs]
[ 931.590335] btrfs_finish_extent_commit+0xe2/0x240 [btrfs]
[ 931.590382] btrfs_commit_transaction+0x573/0x840 [btrfs]
[ 931.590415] ? btrfs_block_rsv_check+0x25/0x70 [btrfs]
[ 931.590456] __btrfs_end_transaction+0x2be/0x2d0 [btrfs]
[ 931.590493] btrfs_end_transaction_throttle+0x13/0x20 [btrfs]
[ 931.590530] btrfs_drop_snapshot+0x489/0x800 [btrfs]
[ 931.590567] btrfs_clean_one_deleted_snapshot+0xbb/0xf0 [btrfs]
[ 931.590607] cleaner_kthread+0x136/0x160 [btrfs]
[ 931.590612] kthread+0x120/0x140
[ 931.590646] ? btree_submit_bio_start+0x20/0x20 [btrfs]
[ 931.590658] ? kthread_bind+0x40/0x40
[ 931.590661] ret_from_fork+0x22/0x40
It seems your filesystem is mounted with the DSICARD option meaning
every delete will result in discard this is highly suboptimal for
ssd's.
Try remounting the fs without the discard option see if it helps.
Generally for discard you want to submit it in big batches (what fstrim
does) so that the ftl on the ssd could apply any optimisations it might
have up its sleeve.
Spot on!
Removed "discard" from fstab and added "ssd", rebooted - no more
btrfs-cleaner running.
Do you know if the issue you described ("discard this is highly
suboptimal for ssd") affects other filesystems as well to a similar
extent? I.e. if using ext4 on ssd?
Would you finally care to share the smart data + the model and make of
the ssd?
2x these:
Model Family: Samsung based SSDs
Device Model: SAMSUNG MZ7LM1T9HCJM-00005
Firmware Version: GXT1103Q
User Capacity: 1,920,383,410,176 bytes [1.92 TB]
Sector Size: 512 bytes logical/physical
Rotation Rate: Solid State Device
1x this:
Device Model: Micron_5200_MTFDDAK1T9TDC
Firmware Version: D1MU004
User Capacity: 1,920,383,410,176 bytes [1.92 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: Solid State Device
Form Factor: 2.5 inches
But - seems the issue was unneeded discard option, so not pasting
unnecessary SMART data, thanks for finding this out.
Tomasz Chmielewski
