Re: Unaligned access in kernel on ARMv6+ (Re: CVS commit: src/sys/dev/usb)

[mlelstv%serpens.de@localhost (Michael van Elst)]

thorpej%me.com@localhost (Jason Thorpe) writes:

>There is a performance penalty for unaligned accesses, and not even all ARM versions can do it in a way that produces the expected results.  The device in question here is a USB device, and we support pre-ARMv6 systems that have USB capability.

The unaligned access is a performance benefit compared to assembling a
result manually byte by byte. This is not the choice between using
aligned vs. unaligned data, the data already comes unaligned as input
and we are talking about the code that reads it.

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                                Michael van Elst
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                                "A potential Snark may lurk in every tree."