Messages in this thread | | | Date | Thu, 18 Jan 2001 19:58:11 +0100 (MET) | From | Roman Zippel <> | Subject | Re: Is sendfile all that sexy? |
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Hi,
On Thu, 18 Jan 2001, Linus Torvalds wrote:
> > Actually, this is a great example, because at one point I was working > > on a device interface which would offload all of the disk-disk copying > > overhead to the disks themselves, and not involve the CPU/RAM at all. > > It's a horrible example. > > device-to-device copies sound like the ultimate thing. > > They suck. They add a lot of complexity and do not work in general. And, > if your "normal" usage pattern really is to just move the data without > even looking at it, then you have to ask yourself whether you're doing > something worthwhile in the first place. > > Not going to happen.
device-to-device is not the same as disk-to-disk. A better example would be a streaming file server. Slowly the pci bus becomes a bottleneck, why would you want to move the data twice over the pci bus if once is enough and the data very likely not needed afterwards? Sure you can use a more expensive 64bit/60MHz bus, but why should you if the 32bit/30MHz bus is theoretically fast enough for your application? So I'm not advising it as "the ultimate thing", but I don't understand, why it shouldn't happen.
bye, Roman
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