Re: Info: NAPI performance at "low" loads
From: Jeff Garzik <hidden>
Date: 2002-09-18 02:32:08
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David S. Miller wrote:
From: Jeff Garzik [off-list ref] 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 :)]