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. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
