Messages in this thread |  | | Date | Tue, 17 Sep 2002 14:58:52 -0700 | From | Andrew Morton <> | Subject | Re: Info: NAPI performance at "low" loads |
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"David S. Miller" wrote: > > 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? >
Looks like it cached it:
- outw(SetIntrEnb | (inw(ioaddr + 10) & ~StatsFull), ioaddr + EL3_CMD); vp->intr_enable &= ~StatsFull; + outw(vp->intr_enable, ioaddr + EL3_CMD);
> 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 :-)
Yup. But deltas are interesting. - 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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