: (And there are certain features of XFS, such as the features that allow
: Irix to tell the disk controller to send disk blocks directly to the
: ethernet controller, which then slaps on the TCP header and calclates
: the TCP checksum without the disk data ever hitting memory
This is not quite right, in fact, it is a little unfair to IRIX. There is
no interaction between the file system and/or the block device system
and the networking stack. The way it works is this (I know this code
extremely well since I'm the guy that originally made NFS use both the
networking and the file system to go at 94MByte/sec - Ethan Solomita is
the guy who made it go at 640MByte/second over Super HIPPI):
I stand corrected. I had heard about the zero copy algorithm you
described, but then when I later heard that Irix had bypassed even the
DMA in and out of memory, I was appropriately horrified. I'm glad to
hear it wasn't true, and that you had no part in implementing or
designing such a horrible hack (i.e., direct device-to-device I/O). :-)
- Ted
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