Messages in this thread | | | Date | Tue, 23 Sep 2003 15:04:59 -0400 | From | Benjamin LaHaise <> | Subject | Re: NS83820 2.6.0-test5 driver seems unstable on IA64 |
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On Tue, Sep 23, 2003 at 11:51:04AM -0700, Grant Grundler wrote: > On Tue, Sep 23, 2003 at 02:29:25PM -0400, Benjamin LaHaise wrote: > ... > > (yet another hardware issue pushed off on software for no significant gain). > > Even x86 pays at least a one cycle penalty for every misaligned access. > In general, open source code has no excuse for using misaligned fields. > It's (mostly) avoidable. TCP/IP headers are the historical exception.
The other point to keep in mind is that apparently the .09u rev of the P4 includes additional hardware for handling unaligned accesses because they are so common (gzip is a good example of an app where it is faster to do an unaligned access for the benefit of fetching the data in one instruction instead of 3+, and there is no way to improve on it).
> One could make the same arguement that a modern NIC should not require > 16 byte alignment for DMA. It's a tradeoff one way or the other. > Just a matter of perspective.
I consider the 83820 buggy in this regard, too. That said, the fix does not belong in the driver layer, as having it duplicated in a dozen drivers is more stupid than fixing up the arch code which is required anyways.
-ben -- "The software industry today survives only through an unstated agreement not to stir things up too much. We must hope this lawsuit [by SCO] isn't the big stirring spoon." -- Ian Lance Taylor, Linux Journal, June 2003 - 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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