On 08/04/2016 02:41 AM, Dave Chinner wrote:
Simple test. 8GB pmem device on a 16p machine:
# mkfs.btrfs /dev/pmem1
# mount /dev/pmem1 /mnt/scratch
# dbench -t 60 -D /mnt/scratch 16
And heat your room with the warm air rising from your CPUs. Top
half of the btrfs profile looks like:
36.71% [kernel] [k] _raw_spin_unlock_irqrestore
¿
32.29% [kernel] [k] native_queued_spin_lock_slowpath
¿
5.14% [kernel] [k] queued_write_lock_slowpath
¿
2.46% [kernel] [k] _raw_spin_unlock_irq
¿
2.15% [kernel] [k] queued_read_lock_slowpath
¿
1.54% [kernel] [k] _find_next_bit.part.0
¿
1.06% [kernel] [k] __crc32c_le
¿
0.82% [kernel] [k] btrfs_tree_lock
¿
0.79% [kernel] [k] steal_from_bitmap.part.29
¿
0.70% [kernel] [k] __copy_user_nocache
¿
0.69% [kernel] [k] btrfs_tree_read_lock
¿
0.69% [kernel] [k] delay_tsc
¿
0.64% [kernel] [k] btrfs_set_lock_blocking_rw
¿
0.63% [kernel] [k] copy_user_generic_string
¿
0.51% [kernel] [k] do_raw_read_unlock
¿
0.48% [kernel] [k] do_raw_spin_lock
¿
0.47% [kernel] [k] do_raw_read_lock
¿
0.46% [kernel] [k] btrfs_clear_lock_blocking_rw
¿
0.44% [kernel] [k] do_raw_write_lock
¿
0.41% [kernel] [k] __do_softirq
¿
0.28% [kernel] [k] __memcpy
¿
0.24% [kernel] [k] map_private_extent_buffer
¿
0.23% [kernel] [k] find_next_zero_bit
¿
0.22% [kernel] [k] btrfs_tree_read_unlock
¿
Performance vs CPu usage is:
nprocs throughput cpu usage
1 440MB/s 50%
2 770MB/s 100%
4 880MB/s 250%
8 690MB/s 450%
16 280MB/s 950%
In comparision, at 8-16 threads ext4 is running at ~2600MB/s and
XFS is running at ~3800MB/s. Even if I throw 300-400 processes at
ext4 and XFS, they only drop to ~1500-2000MB/s as they hit internal
limits.
-chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
