hamachi interrupt coalescing ioctl

[Pete Wyckoff]

Chris said:
> Pete said:
>> I've added a few lines to the hamachi driver to enable changing the
>> parameters regarding interrupt coalescing by an ioctl.
> What's "interrupt coalescing by an ioctl"?

A good example of poor placement of subordinate clauses in a sentence.

Check http://cesdis.gsfc.nasa.gov/linux/drivers/hamachi.html for a short
description of the registers I'm playing with.  They control interrupt
coalescing.  The way I play with the registers is using an ioctl().

Interrupt coalescing is a means by which the NIC can "save up" a bunch of
pending interrupts and deliver them to the host all at once, avoiding the
overhead of processing each one individually.  This comes at the expense
of increased per-packet latency, though.

The tradeoff is CPU usage against packet latency.  Adding this ioctl()
makes it easier to control that tradeoff during a connection, as opposed
to just at module insertion time.

		-- Pete
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