[...] During the IO test, 'dev_active' changed to about 100.Then IO speed got much improve, I got 49.0 MB/s with direct IO. FreeBSD 9.1 give me 50.5 MB/s with direct IO. This test confirmed command queue can improve IO performance dramatically, thank you very much !
Thanks for reporting and testing. I've pushed it to master and MFC'd to 3.4.
Sascha
