For some years, the Kernel Summit has included a panel session where
processor architects from a number of vendors could talk about their plans
and listen to the developers' concerns. Intel's Stephen Fisher started the
discussion with an overview of upcoming processor designs. The processor
roadmap included a number of process and design improvements, mostly aimed
at improving performance, instruction flow, and power management. There
were a lot of low-level hints on how to improve performance on Intel
processors; many of them would probably be more useful to compiler
The IA-64 (Itanium) architecture was never mentioned.
AMD's Rich Brunner is a long time Kernel Summit regular. From his
presentation, AMD is working hard at consolidating its position in the
high-end enterprise market. It's not everybody who needs features like 1GB
pages, 48-bit physical addresses, and quad-core packages. Virtualization
remains high on AMD's agenda; neither of the other two presenters mentioned
it. AMD is also pushing forward on power management, with features like
allowing each CPU on a shared core to be running at a different power
level. He also took the opportunity to let the Summit attendees know that
AMD is looking for Linux kernel hackers.
Freescale Semiconductor was represented by Kate Stewart. Freescale offers
processors based on a number of "IP blocks," with various architectures.
They are mostly working in the embedded market, and would like to see
kernel support for features aimed at that market; these include
asynchronous cryptographic operations, hardware network acceleration, and
faster boot times.
There didn't seem to be a whole lot on the developers' minds during the
general discussion; the coffee, perhaps, had yet to take full effect.
There was some talk of machine check exceptions, which seem to be an
increasing concern as chip features get smaller and faster. There is much
need for improved machine check support which allows the kernel to assess
and contain the damage when something goes wrong. If it is possible to
determine that only a single process is compromised, it is much nicer to
kill that process than to panic the entire system.
Another issue is prefetching of data. Highly optimized code will often
include explicit prefetch instructions, added in the hope of improving
performance by having data in the cache by the time it is needed.
Processors are getting smarter (and more aggressive) about doing their own
prefetching, however, to the point that manually-added prefetches might
actually make things run more slowly. AMD already has a processor mode
which causes it to avoid explicit prefetch commands; Intel may soon follow.
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