The final session on Monday was a brainstorming session, where presenters
had five minutes to raise an issue of interest to them. Here's what came
- James Bottomley talked about I/O operations where use of the I/O
memory management unit is optional. How, he asked, should be block
layer be informed about whether the IOMMU should be used or not?
- Matthew Wilcox discussed a rework of how network devices work, with
all function pointers to be moved into the new netdev_ops
structure. This effort started as a way of eliminating duplicate
implementations of the "ethtool" command set, but then expanded into a
wider effort from there.
- Greg Kroah-Hartman suggested that, in 2.7, static device numbers should
be replaced, since there is no longer any need for them. Instead,
the kernel should allocate truly random device numbers, just to be
sure that nobody ever hard-codes device numbers again. Greg also
suggested that, in 2.7, the kernel should perform device probing in
parallel, speeding up the boot process.
- Adam Belay stated that, in 2.7, he plans to merge resource management
(i.e. control over allocations of I/O ports, I/O memory, and interrupt
numbers) into the device model.
- Sunil Saxena talked about making better use of CPU performance
counters to optimize performance-critical parts of the kernel. He
also mentioned that 64-unit hyperthreaded processors may be on the
- Jon 'maddog' Hall discussed the apparent disconnect between developers and
users at times; users think they have reported a problem, but the
developers have never heard about it. Jon thinks that some effort
needs to go into improving the communications channels.
- William Irwin mentioned that local page replacement policies do not
always produce the best result. In 2.7, he plans to do some
experimenting in that area.
Linus then spoke up, complaining that there has not been anywhere near
enough controversy in the day's discussions. Thus, he concludes, everybody
is perfectly happy with the 2.6 kernel? He asked if there were any
specific worries that anybody would like express regarding the upcoming
It was noted that asynchronous I/O still does not perform well. Linus
responded that AIO has not seen much use or development; it is, essentially,
unused and unmaintained. Unless more people take an interest in AIO, it
will not improve much for 2.6.0.
One developer noted that a great many drivers have not been updated for the
2.5 kernel. Linus acknowledged that drivers are his main worry with this
release. What is really needed here is many, many more testers who will
complain when their particular hardware fails to work. Then the developers
will know which drivers are actually worth the trouble of fixing. But
those testers tend not to come until after the "dot-zero" release. So
2.6.0 will go out with a lot of broken drivers. Eventually (after a year
or so), the ones that never get fixed can be removed.
It was asked: when will the 2.7 development series begin? The soonest
possible time for the 2.7 fork is in about six months; that allows three
more months for the 2.6.0 release, and three more to truly stabilize 2.6.
That is a best-case scenario, however.
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