>>>>> "Donald" == Donald Becker <becker@scyld.com> writes:
Donald> On 9 Feb 2001, Jes Sorensen wrote:
>> The ia64 kernel has gotten mis aligned load support, but it's slow
>> as a dog so we really want to copy the packet every time anyway
>> when the header is not aligned. If people send out 802.3 headers or
>> other crap on Ethernet then it's just too bad.
Donald> Note the word "required", meaning "must be done"
Donald> vs. "recommended" meaning "should be done".
Donald> The initial issue was a comment in a starfire patch that
Donald> claimed an IA64 bug had been fixed. The copy breakpoint
Donald> change might have improved performance by doing a copy-align,
Donald> but it didn't fix a bug.
I agree it was a bug, and yes it has been fixed.
Donald> That performance tradeoff was already anticipated: the
Donald> 'rx_copybreak' value that was changed was a module parameter,
Donald> not a constant. That allows a module-load-time tradeoff,
Donald> based the specific implementation, of copying the received
Donald> packet or accepting a few unaligned loads of the usually small
Donald> IP header. See the comments in starfire.c, as well as several
Donald> other bus-master drivers.
In this case it just results in a performance degradation for 99% of
the usage. What about making the change so it is optimized away unless
IPX is enabled?
Jes
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This archive was generated by hypermail 2b29 : Thu Feb 15 2001 - 21:00:19 EST