Messages in this thread | | | Subject | Re: PATCH: Raw device IO for 2.1.131 | From | Jes Sorensen <> | Date | 14 Dec 1998 11:10:14 +0100 |
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>>>>> "Richard" == Richard Gooch <rgooch@atnf.csiro.au> writes:
Richard> pmonta@halibut.imedia.com writes: >> With a fast disk array it's easy to make this wastage dominate the >> CPU. You remark that this is an evil oddity; I'm not sure I agree. >> Fast I/O buses are nice. I'd *like* to be I/O bound, but it's not >> in the cards with vanilla Linux because the CPU is forced to be >> involved, to no benefit that I can see.
Richard> But isn't this where sendfile(2) is used? The input file is Richard> your disc file and the output file is your network Richard> socket. The kernel triggers the DMA from disc to memory (say Richard> a skbuf) and then triggers the DMA from memory to the network Richard> interface. No cache pollution at all.
Let me point out why I don't like sendfile() then. Most operating systems don't support sendfile() and as such it is a pain in the neck to have to write multiple versions of your software if you run on multiple operating systems. Ie. the software we use here for most of out data transfers is used on at least six different UNIX versions in house and I bet some of the other sites using this software might run it on other flavors.
SGI managed to get zero copy right for write() on a socket and it works great, I'd love having Linux do the same.
Jes
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