Il 15/08/2014 22:15, Paolo Bonzini ha scritto: >> > | Random throughput | Sequential throughput >> > ----------------+-------------------+----------------------- >> > master | 442 MB/s | 730 MB/s >> > base | 453 MB/s | 757 MB/s >> > bypass (Ming) | 461 MB/s | 734 MB/s >> > coroutine | 468 MB/s | 716 MB/s >> > bypass (Paolo) | 476 MB/s | 682 MB/s > This is pretty large, but it really smells like either a setup problem > or a kernel bug...
Thinking more about the I/O scheduler, it could simply be that faster I/O = less coalescing = more bios actually reaching the driver = less speed. It should be possible to find if this is true using blktrace. (The reason why sequential I/O is faster is coalescing in the I/O scheduler). Paolo
