q1.12: phase iii plenary session
DESCRIPTION
Resource: Q1.12 Name: Phase III Plenary Session Date: 09-02-2012 Speaker: David RuslingTRANSCRIPT
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Where are we?
● Community● We're being listened to, our influence is growing
● Operational● Continuous integration process in place● Requirements and roadmap in place
● Technical● We are tackling several heavy lifting problems● Refactoring the ARM Linux kernel towards a unified
kernel tree● LAVA test and validation framework● Android and generic Linux (Ubuntu)● Server coming (along with lots of new architecture)
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Learning Lessons
I learnt these lessons from Tudor Brown (ARM), just retired:● Keep asking yourself – is this what the customer
actually wants?● Don't over engineer the solution; you can never
make it future proof● Phase your approach, three phases, each stable
and with measurable benefits is better than a never-ending engineering project
● Find the simplicity beyond complexity
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The Simplicity Beyond Complexity
The Linaro Mission(s):● Avoid Fragmentation (clear up before the mess)● Power management (10 hour battery life)● Deliver components reliably and on time into
member products
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Testing and Validation
LAVA● How easy is it to deploy it into a
member's IP flow?● We need really deep testing for
the kernel; need to move to scenario driven testing
● Measurable benefits (instrumentation and debug)● Power management● Video, graphics and multimedia
efficiency and tuning
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The (ARM) Linux Kernel
● Continue to refactor the (ARM) Linux Kernel● Lots of code left to shovel and systems to re-engineer
to support ARM Linux● Prevent fragmentation before it happens
● New platforms (A15 and beyond) ● big.LITTLE, Virtualization, Server● Even more kernel influence needed
● Make ARM a key Linux architecture● If not the key architecture
● Get ready for ARMv8!
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Power Management
Challenge: 10 hours is the minimum batter life for a mobile device● We have good foundations - refactoring
cpu_freq / cpu_idle ● Still some arguing around hotswap versus
cpu_idle● LAVA instrumentation necessary to prove
improvements● big.LITTLE is key technology here
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Cortex-A15 Cortex-A7
CCI-400
CPU 1CPU 0 CPU 0 CPU 1
I$ I$ I$ I$D$ D$ D$ D$
L2 Cache + SCU L2 Cache + SCU
GIC-400
Distributor interface
CPU 0Interface
CPU 1Interface
CPU 2Interface
CPU 3Interface
CoreLink CCI-400 Cache Coherent Interconnect
Interrupts
big.LITTLE Overview
Hardware:● High performance A15
cluster● Energy efficient A7 cluster● Coherent interconnectSoftware:● Task Migration (cluster
switching)● MP
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Media Acceleration
● Goal: Integration of all subsystems for the best energy utilization (versus performance) over time● 10 hours battery life playing 3D movies / games
● Difficult because it's OS / distribution specific● Android versus generic Linux
● Linaro should concentrate on the kernel subsystems
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Toolchain
Tuning the base set of tools is great, but...● Need to turn our attention to the whole system● How do we balance computation across all
computing elements for the best battery life?● Is OpenCL the answer or will Android drive
different MP / GPU solutions?● Web languages / applications more and more
important● renderscript
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Back up Slides
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Phase One: Foundation
● We saw problems, we created Linaro ● Build the team(s)● Learn to collaborate across a distributed organisation
● Community● Establish links with the open source communities
● Technical● Consolidate the ARM kernel tree● Engineer toolchain(s) for success
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Phase Two: ...and Empire
● Support mobile products● Embrace Android● Build continuous integration loop and test infrastructure
● Community● Act as a 'center of gravity' for ARM Linux● ARM maintainer's Tree
● Technical● Advanced consolidation● Unified memory management● Power management unification ● Device Tree