On Tue, 29 Dec 2009 03:09:23 am Avi Kivity wrote: > This patch adds a physical block size attribute to virtio disks, > corresponding to /sys/devices/.../physical_block_size. It is defined as > the request alignment which will not trigger RMW cycles. This can be > important for modern disks which use 4K physical sectors (though they > still support 512 logical sectors), and for file-backed disk images (which > have both the underlying filesystem block size and their own allocation > granularity to consider). > > Installers use this to align partitions to physical block boundaries. > > Note the spec already defined blk_size as the performance rather than > minimum alignment. However the driver interpreted this as the logical > block size, so I updated the spec to match the driver assuming the driver > predates the spec and that this is an error. I thought this was what I was doing, but I have shown over and over that I have no idea about block devices. Our current driver treats BLK_SIZE as the logical and physical size (see blk_queue_logical_block_size). I have no idea what "logical" vs. "physical" actually means. Anyone? Most importantly, is it some Linux-internal difference or a real I/O-visible distinction? Rusty. -- 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
