Messages in this thread |  | | Date | Tue, 17 Sep 2002 14:39:47 -0700 (PDT) | Subject | Re: Info: NAPI performance at "low" loads | From | "David S. Miller" <> |
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From: Andrew Morton <akpm@digeo.com> Date: Tue, 17 Sep 2002 14:45:08 -0700
"David S. Miller" wrote: > Well, it is due to the same problems manfred saw initially, > namely just a crappy or buggy NAPI driver implementation. :-) It was due to additional inl()'s and outl()'s in the driver fastpath. How many? Did the implementation cache the register value in a software state word or did it read the register each time to write the IRQ masking bits back?
It is issues like this that make me say "crappy or buggy NAPI implementation"
Any driver should be able to get the NAPI overhead to max out at 2 PIOs per packet.
And if the performance is really concerning, perhaps add an option to use MEM space in the 3c59x driver too, IO instructions are constant cost regardless of how fast the PCI bus being used is :-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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