On Wednesday 29 April 2009, Christoph Hellwig wrote: > On Wed, Apr 29, 2009 at 12:11:19PM +0100, Paul Brook wrote: > > Is this actually measurably faster, or just infinitesimally faster in > > theory? > > On normal disks it's rather theoretical. On high-end SSDs and arrays the > impact is noticeable, mostly due to the additional latency. How exactly does it introduce additional latency? A scsi command block is hardly large or complicated. Are you suggesting that a 16/32byte scsi command takes significantly longer to process than a 16byte virtio command descriptor? I'd expect any extra processing to be a small fraction of the host syscall latency, let alone the latency of the physical host adapter. It probably even fits on the same CPU cache line. Paul -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
