Refactored or_connection_t buffers into cell queues.

Paul Syverson syverson at
Thu Mar 29 03:42:50 UTC 2007

On Wed, Mar 28, 2007 at 11:28:13PM -0400, Cat Okita wrote:
> >6) Cells are about to become the most heavily allocated and freed
> >  structures in Tor.  This is probably going to incur some malloc
> >  overhead, especially on platforms where malloc() sucks.  Since
> >  cells are fixed-size, this arguably calls for arena allocation.
> Somehow cells always reminds me of ATM - looking at queue management
> certainly doesn't hinder that impression.

That's actually where the name comes from. In generation zero onion
routing, our uniform size packets were chosen to be 44 bytes to fit
inside ATM cells. Performance analysis indicated (big surprise) that
I/O performance was terrible with such small cells. They were
increased to 128 bytes (I think, but I might be misremembering) in
generation 1, by the time we got to generation 2 (Tor) they were
substantially larger again, but the original name stuck.


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