Messages in this thread |  | | Date | Tue, 17 Sep 2002 22:36:36 -0400 | From | Jeff Garzik <> | Subject | Re: Info: NAPI performance at "low" loads |
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David S. Miller wrote: > From: Jeff Garzik <jgarzik@mandrakesoft.com> > Date: Tue, 17 Sep 2002 22:11:14 -0400 > > You're looking at at least one extra get-irq-status too, at least in the > classical 10/100 drivers I'm used to seeing... > > How so? The number of ones done in the e1000 NAPI code are the same > (read register until no interesting status bits remain set, same as > pre-NAPI e1000 driver). > > For tg3 it's a cheap memory read from the status block not a PIO.
Non-NAPI:
get-irq-stat ack-irq get-irq-stat (omit, if no work loop)
NAPI:
get-irq-stat ack-all-but-rx-irq mask-rx-irqs get-irq-stat (omit, if work loop) ... ack-rx-irqs get-irq-stat unmask-rx-irqs
This is the low load / low latency case only. The number of IOs decreases at higher loads [obviously :)]
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